Multi-flash photography system

ABSTRACT

A flash photography system having a camera body and external flash devices includes a designating device for designating a sync flash mode for a main flash emission; a first pre-flash emission mode in which the external flash devices are activated to emit a preliminary flash emission at the same time; a second pre-flash emission mode in which the plurality of external flash devices are activated to emit the preliminary flash emission in a predetermined order; a pre-flash emission mode selecting device which selects the first or second pre-flash emission mode in accordance with the designated sync flash mode; and a pre-flash emission command device which transmits a command signal to the external flash devices to emit the preliminary flash emission in the first or second pre-flash emission mode.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a multi-flash photographysystem, wherein the amount of light of the main flash discharge iscontrolled in accordance with photometric readings obtained at apre-flash emission.

[0003] 2. Description of the Related Art

[0004] Various types of multi-flash photography systems in which theamount of light of the main flash discharge is controlled in accordancewith photometric readings obtained at a pre-flash emission (apreliminary flash emission) that is emitted before the main flashdischarge are known in the art. In conventional multi-flash photographysystems, when a plurality of flash devices are activated to emit thepre-flash emission, the calculation for determining the amount of lightof the main flash discharge for each flash device is very complicatedbecause various settings (e.g., an illumination angle setting, a subjectdistance setting, a guide number setting, etc.) on each flash device aregenerally different from those on another flash device In order tosimplify such a calculation, a multi-flash photography system in which aplurality of flash devices are divided into several groups so that thepre-flash emission is emitted by each group of flash devices is alsoknown in the art. However, in the case of using a plurality of slaveflash devices, the flash emission operation of which is controlled via alight signal (wireless command signal) emitted by either an externalflash device connected to the camera or a built-in flash of the camera,the number of such wireless command signals issued by either theexternal flash or the built-in flash (i.e., the number of thelight-signal emissions emitted by the external flash or the built-inflash) increases if the pre-flash emission is emitted by each group offlash devices. This reduces the electrical power efficiency of a batterytherefor.

SUMMARY OF THE INVENTION

[0005] An object of the present invention is to provide a multi-flashphotography system in which the pre-flash emitting operation can becontrolled with a high degree of energy efficiency.

[0006] To achieve the object mentioned above, according to an aspect ofthe present invention, a flash photography system is provided, having acamera body and a plurality of external flash devices electricallyconnected to the camera body, the plurality of external flash devicesbeing activated to emit a preliminary flash emission before a main flashemission. The camera body includes a designating device for designatinga sync flash mode for the main flash emission from among at least onesync flash mode; a first pre-flash emission mode in which the pluralityof external flash devices are activated to emit the preliminary flashemission at the same time; a second pre-flash emission mode in which theplurality of external flash devices are activated to emit thepreliminary flash emission in a predetermined order, and a pre-flashemission mode selecting device which selects one of the first pre-flashemission mode and the second pre-flash emission mode in accordance withthe designated sync flash mode.

[0007] Preferably, the at least one sync flash mode includes asuccessive sync flash mode in which the plurality of external flashdevices are activated to discharge in a predetermined emission sequence,and the pre-flash emission mode selecting device selects the secondpre-flash emission mode in the successive sync flash mode. The pre-flashemission mode selecting device selects the first pre-flash emission modewhen not in said successive sync flash mode.

[0008] Each of the plurality of external flash devices can include async mode request setting device for manually selecting a sync flashmode as a sync mode request, wherein the sync mode request istransmitted to the designating device of the camera body to request theeach external flash device to discharge in the selected sync flash mode.The designating device designates a sync flash mode for the main flashemission in accordance with the sync mode requests set by the sync moderequest setting device of each of the plurality of external flashdevices.

[0009] If the second pre-flash emission mode is selected, the pluralityof external flash devices are activated to emit the preliminary flashemission in the predetermined order in the sync flash mode selectedaccording to the sync mode request.

[0010] Preferably, the designating device designates a sync flash modefor the main flash emission in accordance with the sync mode requestsset by the sync mode request setting device of each of the plurality ofexternal flash devices.

[0011] According to another aspect of the present invention, a flashphotography system having a camera body, at least one external flashdevice which is electrically connected to the camera body, and at leastone slave flash device, wherein the at least one external flash deviceand the at least one slave flash device are activated to emit apreliminary flash emission before a main flash emission. The flashphotography system includes a designating device for designating a syncflash mode for the main flash emission; a first pre-flash emission modein which the at least one external flash device and the at least oneslave flash device are activated to emit the preliminary flash emissionat the same time; a second pre-flash emission mode in which the at leastone external flash device and the at least one slave flash device areactivated to emit the preliminary flash emission in a predeterminedorder; a pre-flash emission command device including a first commanddevice which transmits a first command signal to the at least oneexternal flash device; and a second command device which activates theat least one external flash device to emit a low flash emission servingas a second command signal to transmit the second command signal to theat least one slave flash device; and a pre-flash emission mode selectingdevice which selects one of the first pre-flash emission mode and thesecond pre-flash emission mode. The pre-flash emission mode selectingdevice selects one of the first pre-flash emission mode and the secondpre-flash emission mode in accordance with the sync flash modedesignated by the designating device in the case where only the firstcommand device transmits the first command signal to the at least oneexternal flash device. The pre-flash emission mode selecting deviceselects the second pre-flash emission mode regardless of the sync flashmode designated by the designating device in the case where the secondcommand device activates the at least one external flash device to emitthe low flash emission.

[0012] In an embodiment, if the first pre-flash emission mode isselected, the pre-flash emission command device controls an outputtiming of the first command signal and the second command signal so thatthe at least one external flash device and the at least one slave flashdevice are activated to emit the preliminary flash emission at the sametime.

[0013] Preferably, the second command signal is specified by at leastone time interval of at least two low flash emissions emitted by one ofthe at least one external flash device. The second command deviceactivates the at least one external flash device to emit the low flashemission at an emission interval according to one of the first andsecond the pre-flash emission modes selected by the pre-flash emissionmode selecting device.

[0014] Preferably, the pre-flash emission command device furtherincludes a timer which expires after a predetermined period of time;wherein, in the first pre-flash emission mode, the timer is started,while the at least one external flash device is activated via the secondcommand device to emit the low flash emission serving as the secondcommand signal; the first command signal is transmitted to the at leastone external flash device via the first command device upon expirationof the timer; and the at least one external flash device is activatedagain via the second command device to emit the low flash emission,serving as the second command signal, at the same time the transmissionof the first command signal to the at least one external flash device iscompleted.

[0015] Preferably, the predetermined period of time is determined inaccordance with a duration of the low flash emission which is emitted bythe at least one external device via the second command device, and atime necessary for the first command device to complete the transmissionof the first command signal to the at least one external flash device.

[0016] Preferably, each of the at least one external flash device andeach of the at least one slave flash device includes a sync mode requestsetting device for manually selecting a sync flash mode as a sync moderequest. If the first pre-flash emission mode is selected, the at leastone external flash device and the at least one slave flash device areactivated to emit the preliminary flash emission at the same timeregardless of the sync mode request. If the second pre-flash emissionmode is selected, the at least one external flash device and the atleast one slave flash device are activated to emit the preliminary flashemission in the predetermined order in the selected sync flash mode setas the sync mode request.

[0017] The designating device can designate the sync flash mode for themain flash emission in accordance with the sync mode requests set by thesync mode request setting device of each of the plurality of externalflash devices.

[0018] Preferably, the designating device, the pre-flash emission modeselecting device and the pre-flash emission command device are providedin the camera body.

[0019] Preferably, the designating device, the pre-flash emission modeselecting device and the first command device of the pre-flash emissioncommand device are provided in the camera body, and the second commanddevice of the pre-flash emission command device is provided in the atleast one external flash device.

[0020] According to another aspect of the present invention, a flashphotography system having a camera body is provided, a built-in flashincorporated in the camera body, at least one external flash devicewhich is electrically connected to the camera body, and at least oneslave flash device, wherein the at least one external flash device andthe at least one slave flash device are activated to emit a preliminaryflash emission before a main flash emission. The flash photographysystem includes a designating device for designating a sync flash modefor the main flash emission; a first pre-flash emission mode in whichthe at least one external flash device and the at least one slave flashdevice are activated to emit the preliminary flash emission at the sametime; a second pre-flash emission mode in which the at least oneexternal flash device and the at least one slave flash device areactivated to emit the preliminary flash emission in a predeterminedorder; a pre-flash emission mode selecting device which selects one ofthe first pre-flash emission mode and the second pre-flash emissionmode; a built-in flash emission mode setting device for determiningwhether the built-in flash one of discharges and does not discharge atthe main flash emission, for an exposure operation; and a pre-flashemission command device including a first command device which transmitsa first command signal to the at least one external flash device; and asecond command device which activates one of the built-in flash and theat least one external flash device to emit a low flash emission servingas a second command signal to transmit the second command signal to theat least one slave flash device. The pre-flash emission mode selectingdevice selects one of the first pre-flash emission mode and the secondpre-flash emission mode in accordance with the sync flash modedesignated by the designating device if only the first command devicetransmits the first command signal to the at least one external flashdevice. If the second command device activates one of the built-in flashand the at least one external flash device to emit a low flash emissionwherein the built-in flash emission mode setting device determines thebuilt-in flash to discharge at the main flash emission for an exposureoperation, the pre-flash emission mode selecting device selects thefirst pre-flash emission mode regardless of the sync flash modedesignated by the designating device. If the second command deviceactivates one of the built-in flash and the at least one external flashdevice to emit a low flash emission wherein the built-in flash emissionmode setting device determines the built-in flash not to discharge atthe main flash emission for an exposure operation, the pre-flashemission mode selecting device selects the second pre-flash emissionmode regardless of the sync flash mode designated by the designatingdevice.

[0021] In an embodiment, if the first pre-flash emission mode isselected, the pre-flash emission command device controls an outputtiming of the first command signal and the second command signal so thatthe at least one external flash device and the at least one slave flashdevice are activated to emit the preliminary flash emission at the sametime.

[0022] Preferably, the second command signal is specified by at leastone time interval of at least two low flash emissions emitted by one ofthe at least one external flash device and the built-in flash. Thesecond command device activates one of the built-in flash and the atleast one external flash device to emit the low flash emission at anemission interval according to one of the first and second the pre-flashemission modes selected by the pre-flash emission mode selecting device.

[0023] Preferably, the pre-flash emission command device furtherincludes a timer which expires after a predetermined period of time;wherein, in the first pre-flash emission mode, the timer is started,while one of the built-in flash and the at least one external flashdevice is activated via the second command device to emit the low flashemission serving as the second command signal; the first command signalis transmitted to the at least one external flash device via the firstcommand device upon expiration of the timer; and the one of the built-inflash and at least one external flash device is activated again via thesecond command device to emit the low flash emission, serving as thesecond command signal, at the same time the transmission of the firstcommand signal to the at least one external flash device is completed.

[0024] Preferably, the predetermined period of time is determined inaccordance with a duration of the low flash emission which is emitted bythe at least one external device via the second command device, and atime necessary for the first command device to complete the transmissionof the first command signal to the at least one external flash device.

[0025] Preferably, each of the at least one slave flash device includesa sync mode request setting device for manually selecting a sync flashmode as a sync mode request; a photoreceiver which receives the lowflash emission emitted by the one of the built-in flash and the at leastone external flash device; a measuring device which measures a durationof the low flash emission; a detecting device which determines which ofthe first pre-flash emission mode and the second pre-flash emission modehas been selected, based on whether the duration of low flash emissionis a first duration which represents the first pre-flash emission mode,and determines whether the duration of low flash emission is a secondduration which represents the second pre-flash emission mode; and anemission control device which activates the at least one slave flashdevice to emit the preliminary flash emission simultaneously with thepreliminary flash emission emitted by the at least one external flashdevice regardless of the sync mode request if the first pre-flashemission mode is selected. The sync mode request is transmitted to theemission control device to request the at least one slave flash todischarge in the selected sync flash mode. If the second pre-flashemission mode is selected, the emission control device activates theslave flash device to emit the preliminary flash emission in the syncflash mode selected according to the sync mode request.

[0026] Preferably, the at least one external flash device also includesa sync mode request setting device for manually selecting a sync flashmode as a sync mode request, wherein the sync mode request istransmitted to the designating device to request the corresponding eachexternal flash device to discharge in the selected sync flash mode. Thedesignating device designates the sync flash mode for the main flashemission in accordance with the sync mode requests selected by each ofthe at least one external flash device.

[0027] Preferably, the designating device, the pre-flash emission modeselecting device, the built-in flash emission mode setting device, andthe pre-flash emission command device are provided in the camera body.

[0028] Preferably, the designating device, the pre-flash emission modeselecting device, the built-in flash emission mode setting device, andthe first command device of the pre-flash emission command device areprovided in the camera body, and wherein the second command device ofthe pre-flash emission command device is provided in the at least oneexternal flash device.

[0029] According to another aspect of the present invention, a flashphotography system is provided, having a camera body, a built-in flashincorporated in said camera body, and a plurality of slave flashdevices, the plurality of slave flash devices being activated to emit apreliminary flash emission before a main flash emission. The camera bodyincludes a first pre-flash emission mode in which the plurality of slaveflash device are activated to emit the preliminary flash emission at thesame time; a second pre-flash emission mode in which the plurality ofslave flash device are activated to emit the preliminary flash emissionin a predetermined order; a pre-flash emission mode selecting devicewhich selects one of the first pre-flash emission mode and the secondpre-flash emission mode; a built-in flash emission mode setting devicefor determining whether the built-in flash one of discharges and doesnot discharge at the main flash emission, for an exposure operation; anda pre-flash emission command device which activates the built-in flashto emit a low flash emission serving as a command signal to transmit thecommand signal to the plurality of slave flash device. The pre-flashemission mode selecting device selects the first pre-flash emissionmode, in the case where the built-in flash emission mode setting devicedetermines the built-in flash to discharge at the main flash emissionfor an exposure operation. The pre-flash emission mode selecting deviceselects the second pre-flash emission mode, in the case where thebuilt-in flash emission mode setting device determines the built-inflash not to discharge at the main flash emission for an exposureoperation.

[0030] In an embodiment, the command signal is specified by at least onetime interval of at least two low flash emissions emitted by thebuilt-in flash. The pre-flash emission command device activates thebuilt-in flash to emit the low flash emission at an emission intervalaccording to one of the first and second the pre-flash emission modesselected by the pre-flash emission mode selecting device.

[0031] Preferably, each of the plurality of slave flash device includesa sync mode request setting device for manually selecting a sync flashmode as a sync mode request; a photoreceiver which receives the lowflash emission emitted by the built-in flash; a measuring device whichmeasures a duration of the low flash emission; a detecting device whichdetermines which of the first pre-flash emission mode and the secondpre-flash emission mode has been selected, based on whether the durationof low flash emission is a first duration which represents the firstpre-flash emission mode, and determines whether the duration of lowflash emission is a second duration which represents the secondpre-flash emission mode; and an emission control device which activatesthe slave flash device to emit the preliminary flash emissionsimultaneously with the preliminary flash emission emitted by anotherslave flash device regardless of the sync mode request in the case wherethe first pre-flash emission mode is selected. The sync mode request istransmitted to the emission control device to request the slave flashdevice to discharge in the selected sync flash mode. The emissioncontrol device activates the slave flash device to emit said preliminaryflash emission in the sync flash mode selected according to the syncmode request, in the case where the second pre-flash emission mode isselected.

[0032] According to another aspect of the present invention, a camera isprovided, including at least one terminal connector via which aplurality of external flash devices are electrically connected to thecamera; a designating device for designating a sync flash mode for amain flash emission from among at least one sync flash mode; a firstpre-flash emission mode in which a plurality of flash devices areactivated to emit the preliminary flash emission at the same time beforethe main flash emission; a second pre-flash emission mode in which aplurality of flash devices are activated to emit the preliminary flashemission in a predetermined order before the main flash emission; apre-flash emission mode selecting device which selects one of the firstpre-flash emission mode and the second pre-flash emission mode inaccordance with the designated sync flash mode; and a pre-flash emissioncommand device which commands the plurality of flash devices to emit thepreliminary flash emission in one of the first pre-flash emission modeand the second pre-flash emission mode which is selected by thepre-flash emission mode selecting device.

[0033] Preferably, the at least one sync flash mode includes asuccessive sync flash mode in which the plurality of flash devices areactivated to discharge in a predetermined emission sequence; and thepre-flash emission mode selecting device selects the second pre-flashemission mode in the successive sync flash mode. The pre-flash emissionmode selecting device selects the first pre-flash emission mode when notin the successive sync flash mode.

[0034] Preferably, the pre-flash emission command device includes afirst command device which transmits a first command signal to at leastone external flash device via the terminal connector; and a secondcommand device which activates one of the at least one external flashdevice to emit a low flash emission serving as a second command signalto transmit the second command signal to at least one slave flashdevice. The pre-flash emission mode selecting device selects one of thefirst pre-flash emission mode and the second pre-flash emission mode inaccordance with the designated sync flash mode if only the first commanddevice transmits the first command signal to the at least one externalflash device. The pre-flash emission mode selecting device selects thesecond pre-flash emission mode if the second command device activatesone of the at least one external flash device to emit a low flashemission.

[0035] Preferably, the camera further includes a built-in flashincorporated in the camera; and a built-in flash emission mode settingdevice for determining whether the built-in flash one of discharges anddoes not discharge at the main flash emission, for an exposureoperation. The second command device activates one of the built-in flashand the at least one external flash device to emit a low flash emissionserving as the second command signal. If the second command deviceactivates one of the built-in flash and the at least one external flashdevice to emit a low flash emission wherein the built-in flash emissionmode setting device determines the built-in flash to discharge at themain flash emission for an exposure operation, the pre-flash emissionmode selecting device selects the first pre-flash emission mode. If thesecond command device activates one of the built-in flash and the atleast one external flash device to emit a low flash emission wherein thebuilt-in flash emission mode setting device determines the built-inflash not to discharge at the main flash emission for an exposureoperation, the pre-flash emission mode selecting device selects thesecond pre-flash emission mode.

[0036] In an embodiment, if the first pre-flash emission mode isselected, the pre-flash emission command device controls an outputtiming of the first command signal and the second command signal so thatthe at least one external flash device and the at least one slave flashdevice are activated to emit the preliminary flash emission at the sametime.

[0037] Preferably, the second command signal is specified by at leastone time interval of at least two low flash emissions emitted by one ofthe at least one external flash device and the built-in flash. Thesecond command device activates the at least one external flash deviceto emit the low flash emission at an emission interval according to oneof the first and second the pre-flash emission modes selected by thepre-flash emission mode selecting device.

[0038] Preferably, the pre-flash emission command device furtherincludes a timer which expires after a predetermined period of time;wherein, in the first pre-flash emission mode the timer is started,while one of the built-in flash and the at least one external flashdevice is activated via the second command device to emit the low flashemission serving as the second command signal; the first command signalis transmitted to the at least one external flash device via the firstcommand device upon expiration of the timer; and one of the built-inflash and the at least one external flash device is activated again viathe second command device to emit the low flash emission serving as thesecond command signal, at the same time the transmission of the firstcommand signal to the at least one external flash device is completed.

[0039] Preferably, the predetermined period of time is determined inaccordance with a duration of the low flash emission which is emitted bythe at least one external device via the second command device, and atime necessary for the first command device to complete the transmissionof the first command signal to the at least one external flash device.

[0040] According to another aspect of the present invention, a flashdevice is provided, including a sync mode request setting device formanually selecting a sync flash mode as a sync mode request; aphotoreceiver which receives a low flash emission serving as a commandwhich is emitted by a light source of the camera body; a measuringdevice which measures a duration of the low flash emission; a firstpre-flash emission mode in which the flash device and another at leastone flash device are activated to emit a preliminary flash emission atthe same time; a second pre-flash emission mode in which the flashdevice and the another at least one flash device are activated to emitthe preliminary flash emission in a predetermined order; a pre-flashemission mode selecting device which selects one of the first pre-flashemission mode and the second pre-flash emission mode; a detecting devicewhich determines whether the duration is a first duration whichrepresents the first pre-flash emission mode and further determineswhether the duration of low flash emission is a second duration whichrepresents the first pre-flash emission mode to determine which of thefirst pre-flash emission mode and the second pre-flash emission mode hasbeen selected by the pre-flash emission mode selecting device; and anemission control device which activates the flash device to emit thepreliminary flash emission simultaneously with the preliminary flashemission emitted by the another at least one flash device regardless ofthe sync mode request if the first pre-flash emission mode is selected.The sync mode request is transmitted to the emission control device torequest the at least one slave flash to discharge in the selected syncflash mode. If the second pre-flash emission mode is selected, theemission control device activates the flash device to emit thepreliminary flash emission in the sync flash mode selected according tothe sync mode request.

[0041] The present disclosure relates to subject matter contained inJapanese Patent Applications No.2000-284413 (filed on Sep. 19, 2000) andNo.2001-34579 (filed on Feb. 9, 2001) which are expressly incorporatedherein by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention will be described below in detail withreference to the accompanying drawings in which:

[0043]FIG. 1 is a schematic block diagram of an embodiment of a camerawhich serves as a fundamental component of a flash photography system towhich the present invention is applied;

[0044]FIG. 2 is a circuit diagram of an embodiment of a TTLphotometering circuit shown in FIG. 1;

[0045]FIG. 3 is a circuit diagram of an embodiment of a TTL directphotometering circuit shown in FIG. 1;

[0046]FIG. 4A is a schematic block diagram of a flash device whichserves as a fundamental component of the flash photography system towhich the present invention is applied;

[0047]FIG. 4B is a schematic view of light emitter unit which is drivenin a direction parallel to an optical axis of the camera;

[0048]FIG. 5 is a communication sequence chart for signals transmittedbetween the camera body and the flash device in a state before the flashdevice discharges;

[0049]FIG. 6A is a communication sequence chart for signals transmittedto an external flash device by wire and for a flash emission when a syncmode setting designates the leading curtain sync flash mode and when amode-3 communication is carried out;

[0050]FIG. 6B is a communication sequence chart for signals transmittedto an external flash device by wire and for first and second flashemissions when the sync mode setting designates the successive syncflash mode and when a mode-3 communication is carried out;

[0051]FIG. 6C is a communication sequence chart for a pulse signaltransmitted to an external flash device by wire and for a uniformflash-emission at a time of the main flash exposure when the sync modesetting designates the uniform flash-emission mode and when a mode-4communication is carried out;

[0052]FIG. 6D is a communication sequence chart for a pulse signaltransmitted to an external flash device by wire and for first and secondpre-flash emissions when the flash mode setting designates the pre-flashemission mode and when a mode-4 communication is carried out;

[0053]FIG. 6E is a communication sequence chart for a pulse signalhaving four successive pulses which is output from the camera body to anexternal flash device, and for a wireless signal (a pre-flash emissioncommand wireless signal, a test-flash emission command wireless signalor a uniform flash-emission command wireless signal) transmitted to theslave flash device when a mode-4 communication is carried out;

[0054]FIG. 6F is a communication sequence chart for a pulse signalhaving four successive pulses which is output from the camera body to anexternal flash device, and for a light-magnification command wirelesssignal transmitted to the slave flash device and the light-magnificationcommand wireless signal received by the slave flash device, when theflash mode setting designates the light-magnification flash mode andwhen the mode-4 communication is carried out;

[0055]FIG. 7 is a timing chart for signals or values in the uniformflash-emission process;

[0056]FIG. 8A is a diagram of a photometering area of a TTL nine-segmentphotometering sensor including nine different photometering zones;

[0057]FIG. 8B is a graph showing the distribution of the light receivedby a TTL direct photometering sensor in the horizontal direction acrossthe center of the TTL nine-segment photometering sensor;

[0058]FIG. 8C is a diagram showing the amount of the light received bythe TTL direct photometering sensor via each of the nine differentphotometering zones as a percentage (%) relative to the total amount ofthe light received by the TTL direct photometering sensor;

[0059]FIG. 9A is a conceptual diagram showing a case where the mainobject is located at a position corresponding to only a central part ofthe TTL nine-segment photometering sensor while the background of themain object are located far away from the main object;

[0060]FIG. 9B is a diagram showing the brightness determined with theTTL nine-segment photometering sensor at each of the nine differentphotometering zones thereof in the particular case shown in FIG. 9A atthe pre-flash emission stage;

[0061]FIG. 9C is a conceptual diagram showing a case where the mainobject is located to correspond to a major part of the TTL nine-segmentphotometering sensor while an object having a high reflectivity exits inthe background of the main object;

[0062]FIG. 9D is a diagram showing the brightness determined with theTTL nine-segment photometering sensor at each of the nine differentphotometering zones thereof in the particular case shown in FIG. 9C atthe pre-flash emission stage;

[0063]FIGS. 10A and 10B show a flow chart for a camera main processperformed by a CPU of the camera body;

[0064]FIG. 11 is a flow chart for a flash communication processperformed by the CPU of the camera body;

[0065]FIG. 12 is the first half of a flow chart for a pre-flash emissionprocess performed by the CPU of the camera body;

[0066]FIG. 13 is the second half of the flow chart for the pre-flashemission process;

[0067]FIG. 14 is a flow chart for a pre-flash data determination processperformed by the CPU of the camera body;

[0068]FIG. 15 is a flow chart for a pre-A/D conversion process performedby the CPU of the camera body;

[0069]FIG. 16 is a flow chart for a flash emission amount calculationprocess performed by the CPU of the camera body;

[0070]FIG. 17 is the first half of a flow chart for an exposure processperformed by the CPU of the camera body;

[0071]FIG. 18 is the second half of the flow chart for the exposureprocess;

[0072]FIG. 19 is a flow chart for a test-flash emission processperformed by the CPU of the camera body;

[0073]FIG. 20 is a flow chart for a flash main process performed by aCPU of the flash device;

[0074]FIG. 21 is a flow chart for a wireless mode process performed bythe CPU of the flash device;

[0075]FIG. 22 is a flow chart for a communication interrupt processperformed by the CPU of the flash device;

[0076]FIG. 23 is the first half of a flow chart for a special flashemission process performed by the CPU of the flash device;

[0077]FIG. 24 is the second half of the flow chart for the special flashemission process;

[0078]FIG. 25 is a flow chart for a uniform flash-emission processperformed by the CPU of the flash device;

[0079]FIG. 26 is a flow chart for a normal flash emission processperformed by the CPU of the flash device;

[0080]FIG. 27 is the first half of a flow chart for a PWC interruptprocess performed by the CPU of the flash device;

[0081]FIG. 28 is the second half of the flow chart for the PWC interruptprocess;

[0082]FIG. 29 is a flow chart for a light-magnification flash emissionprocess performed by the CPU of the flash device;

[0083]FIG. 30 is a graph showing the relationship between a flashcontrol time Tm [μs] and a flash emission amount error [EV];

[0084]FIG. 31 is a diagram illustrating the sequence of the A/Dconversion operation performed in the camera body;

[0085]FIG. 32 is a flow chart for an old-system process performed by theCPU of the flash device;

[0086]FIG. 33 is a diagram illustrating the structure of a terminalconnector of the flash device which is connected to a correspondingterminal connector of the camera body;

[0087]FIG. 34 is a circuit diagram of an embodiment of each of fourspecific I/O ports of the CPU of the flash device; and

[0088]FIG. 35 is a timing chart for signals output from specificterminals of the terminal connector of the flash device and for a flashemission in the old-system process, illustrating a Fpulse signal that isoutput from the flash device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0089] An embodiment of a flash photography system which will behereinafter discussed includes a camera body 10 shown in FIG. 1, andmore than one flash device 50 shown in FIG. 4A (only one of them isshown in FIG. 4A). The camera body 10 is an SLR camera body to which aninterchangeable lens (not shown) is mounted. The flash device 50 is usedas either an external flash device which is electrically connected tothe camera body 10 so that the flash operation of the flash device 50 iscontrolled via wire communication between the flash device 50 and thecamera body 10, or a slave flash device whose flash operation iscontrolled by wireless via a low flash emission (wireless signal)emitted by a built-in flash of the camera body 10 or the external flashdevice. The user can freely determine the number of flash devices 50 tobe used, and which flash device 50 is to be used as external flashdevice or slave flash device.

[0090] In the following descriptions, the logic level of a low-level(ground-level) voltage is represented by “0”, while the logic level of ahigh-level voltage is represented by “1” with respect to the illustratedcircuits and elements.

[0091] As shown in FIG. 1, the camera body 10 is provided with a CPU(designating device/pre-flash emission mode selecting device/pre-flashemission command device (first and second command device)/built-in flashemission mode setting device) 13 which serves as a controller forcomprehensively controlling the overall operations of the camera body10. The CPU 13 is provided therein with a RAM 13 a in which control dataare temporarily stored, and a ROM 13 b in which control programs arestored. The voltage of a battery 1 is supplied as a constant voltage Vddto the CPU 13 via a regulator 2. The regulator 2 is provided with aDC/DCon terminal 2 a which serves as a control terminal. The DC/DConterminal 2 a is connected to a port P13 of the CPU 13 so that thevoltage step-up operation of the regulator 2 is controlled by the CPU13. The constant voltage Vdd output from the regulator 2 is alsosupplied to a capacitor 3.

[0092] The camera body 10 is provided with an information display panel5 such as an LCD panel, an EEPROM 6, a camera-lens communicationinterface 7, and a camera-flash communication interface B. Theinformation display panel 5 is connected to a group of ports Ps of theCPU 13, and indicates various photographic information. Variousrewritable parameters and modes are written in the EEPROM 6 that isconnected to a group of ports Pr of the CPU 13. The camera-lenscommunication interface 7 is connected to a group of ports Pp of the CPU13, and is used for communication between the camera body 10 and theinterchangeable lens (not shown) which is mounted to the camera body 10.The camera-flash communication interface 8 is connected to a group ofports Po of the CPU 13, and is used for communication between the camerabody 10 and the external flash device.

[0093] The camera-flash communication interface 8 is provided with aterminal connector 4 provided, e.g., at a hot shoe of the camera body10. The terminal connector 4 has five terminals C, R, Q, X and G. Theterminal C serves as a control terminal via which a control signal isoutput to the external flash device (flash device 50). The terminal Rserves as a clock terminal via which a clock signal is output to theexternal flash device. The terminal Q is a dual-purpose terminal whichis used for the two-way communication between the camera and theexternal flash device, and for outputting a quench signal to theexternal flash device. The terminal X corresponds to the X contact whichbecomes “0” upon completion of a movement of the leading curtain (firstblind) of a focal plane shutter provided in the camera body 10. Theterminal G serves as a ground terminal.

[0094] The camera body 10 is provided with a photometering switch SWS, arelease switch SWR, a main switch SWM and a group of information settingswitches 9 which are connected to the CPU 13 via ports P12, P11, P10 anda group of ports Pn, respectively.

[0095] The photometering switch SWS is turned ON when the release button(not shown) on the camera body 10 is depressed halfway down, while therelease switch SWR is turned ON when the release button is fullydepressed.

[0096] The main switch SWM is turned ON and OFF when a power button orknob (not shown) on the camera body 10 is switched to an ON position andan OFF position, respectively.

[0097] The group of information setting switches 9 includes a test-flashsetting switch, a DX-code information setting switch, a photographicinformation setting switch and a WLint-mode setting switch.

[0098] In the WLint mode, the flash operation of the slave flash device(flash device 50) is wireless-controlled via a light signal (wirelesssignal) emitted by the built-in flash of the camera body 10. The WLintmode has the following subordinate modes: a WLoff mode in which theflash operation of the slave flash device is disabled; a WLFP mode inwhich the slave flash device is activated to discharge in a uniformflash-emission mode (flat emission mode) upon receipt of theaforementioned wireless signal; a WLC mode in which the slave flashdevice is activated to discharge in a normal flash emission mode (i.e.,in a flash emission mode other than the flat emission mode) upon receiptof the aforementioned wireless signal; and a WLM mode in which the slaveflash device is activated to discharge in the normal flash emissionmode, upon receipt of the aforementioned wireless signal, and at thesame time, the built-in flash of the camera body 10 is emitted for anexposure. Note that the use of the term “uniform intensity” or “uniformflash-emission” refers to one kind of flash emission control used inhigh-speed synchronized photography, and can be also referred to as“flat emission”.

[0099] The camera body 10 is provided with a built-in flash circuit 14for activating an xenon flashtube 21, a motor control circuit 15 forcontrolling operations of motors such as a film transport motor, a filmcharge motor and an AF motor, an AF circuit 16 for detecting a focusstate of an image of the object using a phase difference detectingmethod, a diaphragm control circuit 17 for opening and closing an irisdiaphragm of the photographing lens, and a shutter control circuit 18for controlling the movement of the leading and trailing curtains (firstand second curtains) of the focal plane shutter. The built-in flashcircuit 14, the motor control circuit 15, the AF circuit 16, thediaphragm control circuit 17 and the shutter control circuit 18 areconnected to groups of ports Pt, Pu, Ph, Pi and Pj of the CPU 13,respectively. The built-in flash circuit 14 and the xenon flashtube 21are fundamental elements of the built-in flash of the camera body 10. Inthe descriptions of the present specification and claims, the term“built-in flash” represents the xenon flashtube 21 itself or acombination of the built-in flash circuit 14 and the xenon flashtube 21.

[0100] The camera body 10 is provided with a TTL photometering circuit(photometering circuit) 19 and a TTL direct photometering circuit(direct photometering circuit) 20 which are connected to a group ofports Pk and a group of ports Pm of the CPU 13, respectively.

[0101] The camera body 10 is provided with a nine-segment photometeringsensor (a multi-zone photometering sensor) 22 which is disposed in thevicinity of a pentagonal prism (an erecting optical system) (not shown)to receive light passing through an optical path of a viewfinder (notshown). The TTL photometering circuit 19 processes sensor data outputfrom the nine-segment photometering sensor 22, and outputs the processedsensor data to the CPU 13. The nine-segment photometering sensor 22 hasnine different zone sensors 22_1, 22_2, 22_3, 22_4, 22_5, 22_6, 22_7,22_8 and 22_9. The nine-segment photometering sensor 22 can perform aphotometering operation on each of nine different photometering zones (1through 9; see FIG. 8A) defined in the image via the nine zone sensors22_1 through 22_9, respectively.

[0102] The camera body 10 is provided with a TTL direct photometeringsensor (photodiode/single-segment direct photometering sensor) 23 whichis disposed at a position where the TTL direct photometering sensor 23can receive light which is passed through the photographing lens andreflected by a film surface, so that the TTL direct photometering sensor23 can receive light of the object directly during an exposure. The TTLdirect photometering circuit 20 processes a photo-current output fromthe TTL direct photometering sensor 23, and outputs the processed datato the CPU 13.

[0103] In the present embodiment of the flash photography system, thereflected light of a pre-flash emission, which is emitted before themain flash, is photometered by the nine-segment photometering sensor 22to determine a TTL correction value in accordance with the amount ofreceived light at each of the nine different zone sensors 22_1 through22_9. Thereafter, a predetermined optimum exposure amount is correctedin accordance with the TTL correction value, and subsequently thereflected light of the main flash emission is photometered by the TTLdirect photometering sensor 23 to attain correct exposure at a shutterrelease. The reflected light of a test-flash emission that is performedto check the illumination range is photometered via the nine-segmentphotometering sensor 22.

[0104] The TTL photometering circuit 19 will be hereinafter discussed indetail with reference to FIG. 2.

[0105]FIG. 2 is a circuit diagram of an embodiment of the TTLphotometering circuit 19. It should be noted that third through eighthzone sensors 22_3 through 22_8 and associated operational amplifiers andcompressor diodes are not shown in FIG. 2 for the purpose of simplifyingthe drawing. Each of the nine different zone sensors 22_1 through 22_9(only 22_1, 22_2 and 22_9 are shown in FIG. 2) are connected between theinverting input terminal and the non-inverting input terminal of acorresponding one of nine operational amplifiers 100 a through 100 i(only 100 a, 100 b and 100 i are shown in FIG. 2). A reference voltageVs is applied to the non-inverting input terminal of each of the nineoperational amplifiers 100 a through 100 i.

[0106] The light which is incident on the nine-segment photometeringsensor 22 is received thereby at each of the nine different zone sensors22_1 through 22_9, and each of the nine different zone sensors 22_1through 22_9 generates a photo-current corresponding to the amount ofthe received light. The photo-current generated by each of the ninedifferent zone sensors 22_1 through 22_9 is converted logarithmicallyvia a corresponding one of nine compressor diodes 101 a through 101 i(only 101 a, 101 b and 101 i are shown in FIG. 2) to be output to aselector 102. The selector 102 selects one of the nine different zonesensors 22_1 through 22_9 which corresponds to the levels of signalsinput from a group of ports Pk including first through four ports Pk1through Pk4. The photo-current (logarithmic value) generated by one zonesensor selected by the selector 102 is output, as an output V1 of theselector 102, to the non-inventing input terminal of an operationalamplifier 105.

[0107] A constant-current source 103 is connected between the invertinginput terminal of the operational amplifier 105 and ground, while acompressor diode 104 is connected between the non-inverting inputterminal of the operational amplifier 105 and the output terminal of theoperational amplifier 105. Output V2 of the operational amplifier 105 isdetermined via the following equation:

V2=Vs+(KT/q)(ln(Is/Ip))

[0108] wherein

[0109] “T” represents the absolute temperature (temperature in kelvin);

[0110] “K” represents Boltzmann's constant;

[0111] “q” represents the electric charge of electrons;

[0112] “Is” represents the value of the current supplied from theconstant-current source 103; and

[0113] “Ip” represents the photocurrent (logarithmic value) generated byone of the nine different zone sensors 22_1 through 22_9 which isselected by the selector 102.

[0114] The output V2 of the operational amplifier 105 is input to theinverting input terminal of an operational amplifier 109 via a PTC(positive temperature coefficient) thermal resistor 106. The referencevoltage Vs is applied to the non-inverting input terminal of anoperational amplifier 109. A resistor 107 is connected between theinverting input terminal of the operational amplifier 109 and ground,while a resistor 108 is connected between the inverting input terminalof the operational amplifier 109 and the output terminal of theoperational amplifier 109. Assuming that the voltages of the PTC thermalresistor 106, the resistor 108 and the resistor 107 are R1, R2 and R3,respectively, a voltage output V3 of the operational amplifier 109 isdetermined by the following equation:

V3=Vs(1+R2/R3)+(KT/q)(R2/R1)(ln(Is/Ip)).

[0115] In this equation, the absolute temperature is made up for by thetemperature coefficient of the resistor R1. Namely, the output V3 of theoperational amplifier 109 becomes proportional to the photocurrent Ipgenerated by the selected one of the nine different zone sensors 22_1through 22_9, which is selected by the selector 102. The output V3 isoutput to an A/D conversion port Pk5 of the CPU 13.

[0116] The TTL direct photometering circuit 20 will be hereinafterdiscussed in detail with reference to FIG. 3. FIG. 3 is a circuitdiagram of an embodiment of the TTL direct photometering circuit 20. TheTTL direct photometering sensor 23 is connected between the two inputterminals of an operational amplifier 202. An integrating capacitor 201and a MOSFET (metal oxide semiconductor FET) 200, which is hereinafterreferred to as “MOS_SW”, are connected in parallel between the invertinginput terminal of the operational amplifier 202 and the output terminalof the operational amplifier 202. The gate of the MOS_SW 200 isconnected to a port Pm3 of the group of ports Pm of the CPU 13 so thatthe operation of the gate of the MOS_SW 200 is controlled by the CPU 13.More specifically, the operation of the gate of the MOS_SW 200 iscontrolled by the CPU 13 so that the MOS_SW 200 is switched ON and OFFwhen the output of the port Pm3 is “1” and “0”, respectively. In an ONstate of the MOS_SW 200, the integrating capacitor 201 discharges whilethe output voltage of the operational amplifier 202 drops. In an OFFstate of the MOS_SW 200, upon a discharge of the main flash, the TTLdirect photometering sensor 23 receives light reflected by film surfaceto output a photocurrent, and subsequently the integrating capacitor 201integrates (accumulates) the photocurrent corresponding to the amount oflight received by the TTL direct photometering sensor 23. As a result,the output voltage of the operational amplifier 202 rises.

[0117] The output terminal of the operational amplifier 202 is connectedto an input terminal of a comparator 203. The comparator 203 comparesthe output of the operational amplifier 202 with a predetermined voltageT_ttl(x) to output an output signal corresponding to the result of thecomparison. The comparator 203 outputs an output signal of “0” if theoutput of the operational amplifier 202 is equal to or smaller than thepredetermined voltage T_ttl(x). The comparator 203 outputs an outputsignal of “1” if the output of the operational amplifier 202 is greaterthan the predetermined voltage T_ttl (x). The CPU 13 supplies thepredetermined voltage T_ttl (x) to another input terminal of thecomparator 203 via a D/A conversion port Pm1 of the group of ports Pm ofthe CPU 13.

[0118] The output signal of the comparator 203 is input via a resistor204 to an emitter-follower logic circuit consisting of a transistor 206and a resistor 207. The emitter of the transistor 206 is connected tothe terminal Q of the terminal connector 4. The output signal of theemitter functions as a quench signal for quenching the discharge of theexternal flash device. Immediately after the output of the transistor206 changes from low to high, the signal at terminal Q changes from “0”to “1” to quench the discharge of the external flash device. If a syncmode setting designates a successive sync flash mode (the details ofwhich will be discussed later), the signal at terminal Q changes from“1” to “0” immediately after the output of the transistor 206 changesfrom high to low to activate the external flash device which is todischarge after another flash device 50 discharges.

[0119] The transistor 206 is driven between high and low by the CPU 13via a port Pm2 thereof. The CPU 13 usually outputs a signal from theport Pm2 to control the high/low state of the transistor 206. However,in the case where a TTL photometering mode (e.g., TTL Auto-flash mode)is selected as a photometering mode setting, the port Pm2 of the CPU 13serves as an input port. In this case, the transistor 206 is drivenbetween high and low by the output signal of the comparator 203.

[0120]FIG. 4A is a schematic block diagram of the flash device 50. Theflash device 50 is a zoom flash which can adjust the flash illuminationangle in accordance with the focal length of the lens in use. The flashdevice 50 is used as an external flash device or a slave flash device asdescribed above. The flash device 50 serves as external flash devicewhen mounted directly on the camera body 10 (e.g., at a hot shoethereof) or when connected to the camera body via a connecting cord, orserves as slave flash device when not connected to the camera body 10.

[0121] The flash device 50 is provided with a flash CPU 65 (measuringdevice/detecting device/emission control device/built-in flash emissionmode setting device) which serves as controller for comprehensivelycontrolling the overall operations of the flash device 50. The flashdevice 50 is provided with a battery 51, a Schottky diode 52, acapacitor 53 and a regulator 54. The voltage on the battery 51 issupplied as a constant voltage Vdd1 to the flash CPU 65 via the Schottkydiode 52 and the regulator 54. The voltage on the battery 51 is alsosupplied to the capacitor 53 via the Schottky diode 52.

[0122] The flash device 50 is provided with a motor drive/detectingcircuit 62, an EEPROM 60, and a camera-flash communication interface 59,which are connected to the flash CPU 65 via groups of ports Pb, Pc andPd thereof, respectively. A zoom motor 61 of the flash CPU 65 is drivenvia the motor drive/detecting circuit 62. Various rewritable parametersand modes are written in the EEPROM 60. The camera-flash communicationinterface 59 is used for communication between a camera body and theflash device 50.

[0123] As shown schematically in FIG. 4B, the zoom motor 61 serves as azoom driver for moving a light emitting unit 55. The light emitting unit55 includes a xenon flashtube 82, a reflector 55 c and a protectionglass 55 b, and is guided along an axis parallel to an optical axis ofthe camera body 10. Moving the light emitting unit 55 forward andrearward (left and right as viewed in FIG. 4B) with respect to a Fresnellens 55 a positioned in front of the light emitting unit 55 causes thespace between the Fresnel lens 55 a and the light emitting unit 55 tovary to thereby change the flash illumination angle.

[0124] The camera-flash communication interface 59 is provided with aterminal connector 56 which is connected to the terminal connector 4provided on the camera body 10, e.g., at the hot she thereof when theflash device 50 is used as an external flash device. The terminalconnector 56 has five terminals C, R, Q, X and G. The terminal C of theterminal connector 56 serves as a control terminal via which a controlsignal is input from the camera body 10. The terminal R of the terminalconnector 56 serves as a clock terminal via which a clock signal isinput from the camera body 10. The terminal Q of the terminal connector56 is a dual-purpose terminal which is used for two-way communicationbetween the camera body 10 and the flash device 50, and for inputting aquench signal for the flash device 50 from the camera body 10. A signalfrom the X contact of the camera body 10 is input from the camera body10 via the terminal X of the terminal connector 56. The terminal G ofthe terminal connector 56 serves as a ground terminal.

[0125] In a state where the flash device 50 is connected to the camerabody 10 via the terminal connectors 4 and 56, the flash CPU 65 carriesout data-communication with the camera body 10 via the terminals C, Rand Q.

[0126] The terminals C, R and Q of the terminal connector 56 areconnected to ports Pd1, Pd2 and Pd3 of the group of ports Pd of theflash CPU 65 via the camera-flash communication interface 59,respectively (see FIG. 33). In FIG. 33 the camera-flash communicationinterface 59 is not shown for the purpose of simplifying the drawing. Asshown in FIG. 33, the terminal X of the terminal connector 56 isconnected to a port Pd 4 via a diode 400. The diode 400 protects theflash CPU 65 from being damaged if the flash device 50 is connected tothe camera together with an external flash device which causes a highvoltage to be applied to terminal X of the terminal connector 56.

[0127] The flash device 50 is provided with a group of informationsetting switches 63 and a main switch 64. The main switch 64 is asliding switch which takes one of the following three positions: OFF, WL(wireless) and ON. The main switch 64 is provided with a WL terminal andan ON terminal which are connected to the flash CPU 65 via ports P1 andP0 thereof, respectively.

[0128] The group of information setting switches 63 is connected to theflash CPU 65 via the group of ports Pa. The group of information settingswitches 63 includes a photometering mode request setting switch 63 a, async mode request setting switch (sync mode request setting device) 63b, a wireless mode setting switch 63 c, and a system selector switch 63d.

[0129] The photometering mode request setting switch 63 a switches thephotometering mode among the three photometering modes: a TTLphotometering mode, an auto flash photometering mode and a manualphotometering mode, in that order every time the photometering moderequest setting switch 63 a is depressed (switched ON). In the TTLphotometering mode, the flash device 50, servinig as an external flashdevice, stops emitting when the light amount measured by the TTL directphotometering sensor 23 reaches an appropriate receiving light amount.In the auto photometering mode, the flash device 50 stops emitting whenthe light amount measured by the auto flash circuit 71 reaches apredetermined receiving light amount. In the manual photometering mode,the flash device 50 stops emitting after the predetermined time islapsed.

[0130] The sync mode request setting switch 63 b is operated to set oneof the following flash modes as a sync mode request: a leading curtainsync flash mode, the successive sync flash mode and the uniformflash-emission mode (flat emission mode). In the leading-curtain syncflash mode, the flash device 50 starts firing upon completion of amovement of the leading curtain of the shutter. In the successive syncflash mode, the flash device 50 which serves as external flash devicestarts discharging at the trailing edge of the quench signal afteranother flash device 50 which also serves as external flash device andwhich has been set in the leading curtain sync flash mode hasdischarged. In the flat emission mode, the flash fires with asubstantially uniform intensity for a given period of time so as to giveuniform flash-emission on the object in high-speed synchronizedphotography.

[0131] The wireless mode setting switch 63 c is operated to set one ofthe following three wireless modes: a wireless controller mode, awireless master mode and a wireless slave mode. In the wirelesscontroller mode, the flash device 50 controls the operation of at leastone slave flash device (another flash device 50) by wireless control. Inthe wireless master mode, the flash device 50 controls the operation ofat least one slave flash device (another flash device 50) by wirelesscontrol, and at the same time, discharges to emit the main flash at atime of exposure. In the wireless slave mode, the flash device 50 isused as a slave flash device, which is not connected to the camera body10 in use. Accordingly, the wireless controller mode and the wirelessmaster mode can be set only when the flash device 50 is used as anexternal flash device, while the wireless slave mode can be set onlywhen the flash device 50 is used as a slave flash device.

[0132] The wireless mode setting switch 63 c is valid only when the mainswitch 64 is in the aforementioned position WL.

[0133] The system selector switch 63 d is valid only when the flashdevice 50 serves as slave flash device, and is operated to set either anold-system compatible mode or a new-system compatible mode. In theold-system compatible mode, the slave flash device emits the main flashat a time of exposure upon receiving a single flash emission (lightsignal) emitted by the built-in flash of the camera body 10 or theexternal flash device. In the new-system compatible mode, the slaveflash device emits the main flash at a time of exposure upon receivingmore than one light signal (wireless signal) successively.

[0134] The flash device 50 is provided with a wireless light-receivingcircuit 58, an auto flash circuit 70 and an information display panel 72such as an LCD panel which are connected to the flash CPU 65 via groupsof ports Pe, Pf and Pg, respectively. The wireless light-receivingcircuit 58 processes the output of a light-receiving element(photoreceiver) 57 connected to the wireless light-receiving circuit 58.The auto flash circuit 70 processes the output of a light-receivingelement 71 connected to the auto flash circuit 70. The informationdisplay panel 72 indicates various information such asphotometering-range checking information. The light-receiving element57, which is connected to the wireless light-receiving circuit 58,operates to receive a flash emission of the built-in flash or theexternal flash device when the flash device 50 serves as slave flashdevice. The light-receiving element 71, which is connected to the autoflash circuit 70, operates to detect the amount of the main flashemission of the flash device 50 in the auto flash photometering mode.

[0135] The flash CPU 65 is provided with a voltage step up circuit 66which multiplies the voltage of the battery 51, and a state-of-chargedetecting circuit 69. The voltage step up circuit 66 is connected to theflash CPU 65 via a port P2 thereof. The state-of-charge detectingcircuit 69 is connected to the flash CPU 65 via an A/D conversion portPad thereof. The voltage multiplied by the voltage step up circuit 66 issupplied to a main capacitor 79 via a diode 67, and also to thestate-of-charge detecting circuit 69 via a diode 68 at the same time. Aterminal voltage HV across the main capacitor 79 can be detected via thestate-of-charge detecting circuit 69 only when the voltage step upcircuit 66 is in operation.

[0136] The flash device 50 is provided with a 30-volt generating circuit77, a level shift circuit 78 and a trigger circuit 80, which areconnected to ports P4, P5 and P3 of the flash CPU 65, respectively. The30-volt generating circuit 77 generates a voltage of 30 volts outputfrom a terminal 30Vout of the 30-volt generating circuit 77 with theaforementioned terminal voltage HV as a power source if a signal 30Vonwhich is output from the port P4 of the flash CPU 65 to be input to the30-volt generating circuit 77 is “1”. The voltage of 30 volts outputfrom the 30-volt generating circuit 77 is supplied to the level shiftcircuit 78.

[0137] The level shift circuit 78 applies the voltage of 30 volts, whichis supplied from the 30-volt generating circuit 77, to a gate IGBTg ofan IGBT 83 to switch the IGBT 83 ON when the port P5 of the flash CPU 65is “1”, i.e., a signal IGBTon input from the flash control circuit 65 is“1”. On the other hand, the level shift circuit 78 operates to switchthe IGBT 83 OFF when the port P5 of the flash control circuit 65 is “0”,i.e., when the signal IGBTon input from the flash control circuit 65 is“0”.

[0138] The trigger circuit 80 applies an oscillating high voltage to atrigger electrode XeT of the xenon flashtube 82 to render xenon gasfilled therein in an excitation state. In this excitation state, theelectric charges accumulated in the main capacitor 79 are discharged viaa coil 81, the xenon flashtube 82 and the IGBT 83 at the time the IGBT83 is switched ON to thereby activate the xenon flashtube 82 to flash.

[0139] The flash device 50 is provided with a comparator 75, thenon-inverting input terminal of which is connected to a D/A conversionport Pda of the flash CPU 65. The flash device 50 is provided with acapacitor 73 and a resistor 74 which are connected to ports P6 and P7,respectively. A terminal of the capacitor 73 and the resistor 74 isconnected to the inverting input terminal of the comparator 75. Aterminal of a light-receiving element 85 for detecting the amount of theflash emission discharged from the xenon flashtube 82 is also connectedto the inverting input terminal of the comparator 75. Thelight-receiving element 85 is positioned so as to receive the flashemission of the xenon flashtube 82 directly via the protection glass 55b, and outputs a photocurrent corresponding to the amount of thereceived light.

[0140] The comparator 75 compares a predetermined voltage FPlvl inputfrom the D/A conversion port Pda with a voltage PDfl corresponding tothe output of the light-receiving element 85. Subsequently, thecomparator 75 outputs a low-level signal “0” if the voltage PDfl issmaller than the voltage FPlvl, or outputs a high-level signal “1” ifthe voltage PDfl is equal to or greater than the voltage FPlvl. Theoutput of the comparator 75 is supplied to the level shift circuit 78via a resistor 76. The level shift circuit 78 inputs the output of thecomparator 75 as a signal IGBTctl to switch the IGBT 83 ON or OFF.

[0141] The basic structure of the flash device 50 has been discussedabove. The groups of ports Pd (I/O ports Pd1, Pd2, Pd3 and Pd4) of theflash CPU 65 will be hereinafter discussed in detail. FIG. 34 shows anembodiment of each of the ports Pd1, Pd2, Pd3 and Pd4. A port Pd′ shownin FIG. 34 represents each of the ports Pd1, Pd2, Pd3 and Pd4 since allthe ports Pd1, Pd2, Pd3 and Pd4 have the same structure. Accordingly,each of the ports Pd1, Pd2, Pd3 and Pd4 will be hereinafter discussed asthe port Pd′ in detail with reference to FIG. 34.

[0142] The drain of each of a p-channel MOSFET 402, a p-channel MOSFET403 and a n-channel MOSFET 404 is connected to the port Pd′. The sourceof the p-channel MOSFET 402 is connected to a constant-voltage line Vdd1via a pull-up resistor 401, while the gate of the p-channel MOSFET 402is connected to the output terminal of a two-input NOR gate 406. Thesource of the p-channel MOSFET 403 is connected to the constant-voltageline Vdd1, while the gate of the p-channel MOSFET 403 is connected tothe output terminal of a two-input NAND gate 405. The source of then-channel MOSFET 404 is connected to ground, while the gate of then-channel MOSFET 404 is connected to the output terminal of thetwo-input NOR gate 406. One of the two input terminals of the two-inputNOR gate 406 is connected to an I/O port switch terminal IN/OUT, whilethe other input terminal of the two-input NOR gate 406 is connected toan output terminal PdOUT. One of the two input terminals of thetwo-input NAND gate 405 is connected to the output terminal of aninverter 408, while the other input terminal of the two-input NAND gate405 is connected to the output terminal PdOUT. The output of the I/Oport switch terminal IN/OUT is input to the input terminal of theinverter 408. The port Pd′ is connected to an input terminal PdIN via aninverter 407.

[0143] In the above described embodiment of the port Pd′, the n-channelMOSFET 404 is in the OFF state because the output of the two-input NORgate 406 is “0” regardless of the state of the output terminal PdOUTwhen the I/O port switch terminal IN/OUT is “1”. In addition, the outputof the two-input NAND gate 405 is “1”, while the p-channel MOSFET 403 isin the OFF state. Therefore, the signal output from the output terminalPdOUT is not output to a port Pd′. In this case, since the p-channelMOSFET 402 is in the OFF state, the port Pd′ is pulled up by the pull-upresistor 401. Namely, the state of input of the port Pd′ is captured andtaken into the flash CPU 65 from the input terminal PdIN via theinverter 407.

[0144] The signal output from the port Pd′ is “0” when the I/O portswitch terminal IN/OUT is “0” because the n-channel MOSFET 404 and thep-channel MOSFET 403 are in the ON state and the OFF state,respectively, if the output terminal PdOUT is “0”. On the other hand,the signal output from the port Pd′ is “1” when the I/O port switchterminal IN/OUT is “0” because the n-channel MOSFET 404 and thep-channel MOSFET 403 are in the OFF state and the ON state,respectively, if the output terminal PdOUT is “1”. Accordingly, each ofthe group of ports Pd serves as an input port and an output port whenthe I/O port switch terminal IN/OUT is “1” and “0”, respectively.

[0145] On the basis of the above described structures of the camera body10 and the flash device 50, fundamental operations of the camera bodywill be hereinafter discussed with reference to the flow charts shown inFIGS. 10A through 19.

[0146] [Camera Main Process]

[0147]FIGS. 10A and 10B are a flow chart for a camera main processperformed by the CPU 13 of the camera body 10. Immediately after thebattery 1 is loaded in the camera body 10, control enters the cameramain process after the CPU 13 is initialized. In the camera mainprocess, firstly each port of the CPU 13 is initialized (step S100), andthe CPU 13 has communication with the EEPROM 6 to read out initial datatherefrom (step S101). Subsequently, it is determined whether the mainswitch SWM is ON (step S102).

[0148] If the main switch SWM is not ON (if NO at step S102) a mainswitch OFF process is performed (step S106) and subsequently the displayindicated on the information display panel 5 is turned OFF (step S107).The main switch OFF process is performed to stop the voltage step-upprocess of the regulator 2, and to stop the charging operation forcharging the built-in flash if it is in the process of charging.Subsequently, an interrupt of the main switch SWM is enabled (stepS108), and the CPU 13 enters a sleep mode (step S109). In the sleep modeat step S109, since an interrupt of the main switch SWM is enabled, aninterrupt occurs and control returns to the operation at step S100 ifthe main switch SWM is turned ON again.

[0149] If it is determined at step S102 that the main switch is ON (ifYES at step S102), various modes and functions are set in accordancewith the state of each switch of the group of information settingswitches 9 (step S103). Subsequently, the information on the set modesand functions and also various photographic information such as theaforementioned photometering-range checking information are indicated onthe information display panel 5 (step S104). Subsequently, a built-inflash charging process is performed (step S105). In the built-in flashcharging process, it is determined whether the camera body 10 is in apredetermined condition (e.g., a condition that the main switch SWM wasjust turned ON, the built-in flash just discharged, or the retractablebuilt-in flash was just popped up from the retracted position). If thepredetermined condition is satisfied, a capacitor (not shown) providedin the built-in flash circuit 14 for supplying power to the xenonflashtube 21 is charged.

[0150] Subsequently, it is determined whether the photometering switchSWS or the release switch SWR is ON (step S110). If neither thephotometering switch SWS nor the release switch SWR is ON (if NO at stepS110), a main switch ON process is performed (step S116). In the mainswitch ON process, predetermined processes which includes a process ofstopping the voltage step-up operation of the regulator 2 are performedif the built-in flash is not in the process of charging. Subsequently, atimer A set for 125 ms is started (step S117), an interrupt of the timerA is enabled (step S118), and the CPU 13 enters the sleep mode (stepS119). In the sleep mode at step S119, since an interrupt of the timer Ais enabled, an interrupt occurs upon the timer A lapsing, and controlreturns to the operation at step S102. Therefore, in a state where themain switch SWM is ON, and at the same time, both the photometeringswitch SWS and the release switch SWR are OFF, the operations at stepsS102 through S110 and steps S116 through 119 are performed every 125 ms.

[0151] If either the photometering switch SWS or the release switch SWRis ON (if YES at step S110), the output port P13 is changed to “0” tothereby start the voltage step-up operation of the regulator 2 (stepS111). With this operation, the output voltage Vdd of the regulator 2 ismaintained at a constant voltage even if the voltage across the battery1 drops. Subsequently, a camera-lens communication process is performed(step S112). In the camera-lens communication process, the CPU 13communicates with the photographing lens (not shown) mounted on thecamera body 10 via the camera-lens communication interface 7 to readinformation (lens information) of the photographing lens. The lensinformation read at step S112 includes information on an f-number AVminat full aperture, photometering correction information Avc, focal lengthinformation f, and a distance value (distance information) Dv. After thecamera-lens communication process at step S112, a flash communicationprocess (“Flash Communication Process” shown in FIG. 11) in which theCPU 13 communicates with the external flash device via the terminalconnectors 4 and 56 is performed (step S113). In the flash communicationprocess, CF (camera-to-flash) information is output to the externalflash device while FC (flash-to-camera) information (shown in Tables 1and 2) is input from the external flash device.

[0152] Subsequently, an AF process in which the CPU 13 inputs a videosignal from the phase detection type AF circuit 16 to calculate theamount of defocus is performed (step S114). In the AF process, an AFmotor (not shown) is driven by an amount corresponding to the calculatedamount of defocus to move a focusing lens group (not shown) of theinterchangeable lens to an axial position where an in-focus state isobtained. After the AF process is performed, an AE process is performed(step S115). In the AE process, the CPU 13 inputs a photometric signalcorresponding to the output of the TTL nine-segment photometering sensor22 from the TTL photometering circuit 19 to determine an optimum shutterspeed and an optimum aperture value in accordance with the inputphotometric signal, the current exposure mode, lens information andflash information. In the AE process it is determined whether the flashdevice 50 needs to discharge at a shutter release.

[0153] After the AE process is performed, it is determined whether therelease switch SWR is ON (step S120). Control returns to step S102 ifthe release switch SWR is not ON (if NO at step S120). If the releaseswitch SWR is ON (if YES at step S120), a release condition determiningprocess in which it is determined whether a predetermined releasecondition is satisfied is performed (step S121). The predeterminedrelease condition can be, e.g., a condition wherein the object is infocus if an in-focus priority mode has been set as an AF exposure mode.Alternatively, the predetermined release condition can be a conditionwherein the built-in flash has been fully charged if a releaseprohibition mode, in which a shutter release is prohibited if the objectbrightness is low and the built-in flash has not been fully charged, hasbeen selected as a photographic mode.

[0154] If the aforementioned release condition is not satisfied (if NOat step S122), control returns to step S102. If the aforementionedrelease condition is satisfied (if YES at step S122), the flashcommunication process (“Flash Communication Process” shown in FIG. 11)is again performed as a final flash communication process before ashutter release (step S123). Subsequently, it is determined whether apre-flash emission is necessary, i.e., whether a PreNeed flag is 1. Ifthe PreNeed flag is 1 (if YES at step S124), a pre-flash emissionprocess (“Pre-Flash Emission Process” shown in FIGS. 12 and 13) isperformed (step S125) If the PreNeed flag is 0 (if NO at step S124),control skips the pre-flash emission process, thus proceeding straightfrom step S124 to step S126.

[0155] At step S126 a mirror-up process in which a mirror motor (notshown) is actuated via the motor control circuit 15 to move up aquick-return mirror (not shown) is performed. Subsequently, an irisdiaphragm (not shown) of the interchangeable lens is stopped down (stepS127) via the iris-diaphragm control circuit 17 by an amountcorresponding to the aperture value determined in the AE process.Subsequently, an exposure process (exposure operation) is performed(step S128) (“Exposure Process” shown in FIGS. 17 and 18). In theexposure process, the focal plane shutter is released via the shuttercontrol circuit 18 in accordance with the shutter speed determined inthe AE process. Subsequently, upon the completion of the operation ofthe focal plane shutter, a mirror-down/charge process and a film windingprocess are performed (step S129). In the mirror-down/charge process,the mirror motor is driven to return the quick-return mirror back to theinitial position. In the film winding process, a film motor is driven towind a film by one frame. Subsequently, control returns to step S102.

[0156] [Flash Communication Process]

[0157] The flash communication process performed at steps S113 and S123will be hereinafter discussed in detail with reference to FIG. 11. Inthis process, firstly the CPU 13 performs an FC communication in whichthe CPU 13 has communication with the flash CPU 65 of the external flashdevice to input FC information (shown in Tables 1 and 2) from theexternal flash device (step S150). Initial data of the FC communicationincludes a specified code. If the CPU 13 cannot receive the specifiedcode properly, the CPU 13 determines that an external flash device isnot coupled to the camera body 10. In this case, the CPU 13 does notperform any communication operation in any one of the followingcommunications: a CF communication, a mode-4 communication and a mode-3communication.

[0158] After the FC communication is performed, it is determined whethera WLreq flag is 1 (step S151). The WLreq flag is set to 1 if the mainswitch 64 is in the WL (wireless) position and if the wireless modesetting switch 63 c is in the position of either the wireless controllermode or the wireless master mode. If the WLreq flag is 1 (if YES at stepS151), a WLset flag is set to 1 (step S153). The WLset flag is set to 1when the slave flash device is controlled by wireless via the externalflash device. Subsequently, a WLint flag is set to 0 (step S156), andcontrol proceeds to step S157. The WLint flag is set to 1 when the slaveflash device is controlled by wireless via the built-in flash of thecamera body 10. In the present embodiment, since the WLint flag isalways set to 0 at step S156 if the WLset flag is set to 1 at step S153,the WLint flag and the WLset flag never become 1 at the same time. Thewireless control using the built-in flash as a wireless remotecontroller is effective only when a wireless control using the externalflash device as a wireless remote controller is not performed.

[0159] If the WLreq flag is not 1, namely, if no external flash device50 is connected to the camera body 10 or if the main switch 64 of theexternal flash device 50 connected to the camera body 10 is not in theWL position (if NO at step S151), the WLset flag is set to 0 (stepS152). Subsequently, it is determined whether the WLoff mode, in whichthe flash operation of the slave flash device is disabled, is currentlyset and whether the built-in flash has been fully charged (step S154).If the WLoff mode has not been set and if the built-in flash has beenfully charged (if YES at step S154), the WLint flag is set to 1 (stepS155). On the other hand, if the Wboff mode has been set or if thebuilt-in flash has not been fully charged (if NO at step S154), theWLint flag is set to 0 (step S156) and control proceeds to step S157.

[0160] It is determined at step S157 whether each of the WLset flag andthe WLint flag is 0. If no slave flash device is controlled by wirelessvia either the built-in flash or external flash device (if YES at stepS157), it is determined via a charge completion signal included in theFC information input at step S150 whether the external flash device hasbeen fully charged (step S158). If the external flash device has notbeen fully charged, the TTL photometering mode is selected as aphotometering mode setting, while the PreNeed flag is set to 0 (stepS161), and control proceeds to step S162. If either the WLset flag orthe WLint flag is not 0 (if NO at step S157), control proceeds to stepS159. If the external flash device has been fully charged (if YES atstep S158), control proceeds to step S159.

[0161] At step S159 the PreNeed flag is set to 1. Subsequently, the syncmode setting, a pre-flash emission mode PreM and the photometering modesetting are determined with reference to Tables 4-1, 4-2 and 4-3 inaccordance with the sync mode request, the charge completion signal andwhether or not the slave flash device is controlled by wireless (stepS160). The details of this process at step 160 will be discussed later.The pre-flash emission mode PreM includes a first pre-flash emissionmode in which all the flash devices except the built-in flash areactivated to emit a pre-flash at the same time, and a second pre-flashemission mode in which all the flash devices except the built-in flashare activated to emit a pre-flash in a predetermined order. Thepre-flash emission mode PreM is set to 0 if the first pre-flash emissionmode is set, or 1 if a second pre-flash emission mode is set.

[0162] After the process at step S160, a uniform flash-emission durationTfp (ms) is set (step S162). The uniform flash-emission duration Tfp(ms) is calculated at step S162 using the following equation:

Tfp=1/2^(Tv) +Tctn

[0163] wherein Tctn represents the duration of a movement of the leadingcurtain of the focal plane shutter; and APEX value Tv represents thetime value (shutter speed).

[0164] Subsequently, a maximum flash photometering distance Dvmax is set(at step S163). The maximum flash photometering distance Dvmax isdetermined from the following equation:

Dvmax=Gv−Av+(Sv−5)

[0165] wherein Dvmax represents the distance value according to the APEXsystem; Gv represents the guide number value according to the APEXsystem; Av represents the aperture value according to the APEX system;and Sv represents the film speed value according to the APEX system.

[0166] Subsequently, the focal length information f included in the lensinformation read at step S112 is set (step S164). Thereafter, the CFcommunication, in which the CF information determined in the abovedescribed processes is transmitted to the external flash device, isperformed (step S165).

[0167] After the CF communication is performed, a wireless signalinterval TW1M is set so as to correspond to the currently-set flash modesetting, and is stored in the RAM 13 a via operations at steps S166-1through S166-5. The wireless signal interval TW1M, which is stored inthe RAM 13 a, represents the time interval at which the built-in flashor the external flash device is activated to emit two successive lowflash emissions serving as a wireless signal (a pre-flash emissioncommand wireless signal) which is transmitted to the slave flash device.The slave flash device reads the command provided by the wireless signalin accordance with the wireless signal interval TW1M.

[0168] After the CF communication is performed, firstly, it isdetermined at step S166-1 whether the sync mode setting designates theflat emission mode (the uniform flash-emission mode). If the sync modesetting designates the flat emission mode (if YES at step S166-1), thewireless signal interval TW1M is set to 5.2 ms (step S166-2), andcontrol proceeds to step S167. If the sync mode setting does notdesignate the flat emission mode (if NO at step S166-1), it isdetermined whether the pre-flash emission mode PreM is 1 (step S166-3).If the pre-flash emission mode PreM is 1 (if YES at step S166-3) thewireless signal interval TW1M is set to 4.2 ms (step S166-4), andcontrol proceed to step S167. If the pre-flash emission mode PreM is not1 (if NO at step S166-3), the wireless signal interval TW1M is set to3.2 ms (step S166-5).

[0169] It is determined at step S167 whether the test-flash settingswitch of the group of information setting switches 9 has been switchedfrom OFF to ON (step S167). If the test-flash setting switch has beenswitched from OFF to ON (if YES at step S167), a test-flash emissionprocess (“Test-Flash Emission Process” shown in FIG. 19) is performed(step S168), and control returns to the camera main process. If thetest-flash setting switch has not been switched from OFF to ON (if NO atstep S167), control skips the operation at step S168 and returns to thecamera main process.

[0170] Table 1 below shows an embodiment of the FC information which istransmitted from the external flash device to the camera body 10. TABLE1 No. FC INFORMATION CONTENT 1 Charge Completion Signal Charge 2Photometering Mode Request TTL, Auto, Manual 3 Sync Mode Request LeadingCurtain, Successive Sync Flash, Flat Emission 4 Wireless Mode RequestWLreq 5 Gno Gv 6 Photometering Range Check Correct, Far, Near 7 BounceBounce

[0171] In Table 1, data corresponding to a photometering mode (a TTLphotometering mode, the auto flash photometering mode or a manualphotometering mode) having been set on the external flash device is setas a photometering mode request. Wireless mode request is represented bythe WLreq flag. The guide number value (APEX value) Gv which representsa guide number Gno corresponding to the illumination angle of theexternal flash device is set as Gno information. “Correct”, “Near” or“Far” is set as the photometering-range checking information inaccordance with a time from the moment the external flash device inputsa flash start command from the camera body 10 to the moment the externalflash device inputs a flash stop command from the camera body 10 whenthe external flash device discharges. A Bounce flag which representsbounce information is set at 1 when a head of the external flash deviceis tilted or swiveled upward to give a bounce flash to the object.

[0172] Table 2 below shows an embodiment of data of the sync moderequest and the charge completion signal. TABLE 2 Bit No. 3 2 1 0 ChargeCurtain WL Flat Successive Leading Completion (Wireless) Emission SyncFlash Curtain Signal Sync Mode Flat Successive Leading Request EmissionSync Flash Curtain

[0173] Three-bit data defines the sync mode request. One of the threebit positions of the three-bit data, which corresponds to the sync moderequest set on the external flash device, is set to 1. On the otherhand, four-bit data defines the charge completion signal. One of thefour bit positions of the four-bit data which corresponds to the syncmode request is set to 0 if the flash charging has been completed. Thecharge completion signal of “1” takes precedence over the chargecompletion signal of “0” For instance, in the case where more than oneexternal flash device with the same sync mode request is connected tothe camera body 10, the aforementioned one of the four bit positions ofcharge completion signal, which corresponds to the sync mode request, isset to 0 only when all the external flash devices connected to thecamera body 10 have been fully charged. Bit 3 of the charge completionsignal is provided for wireless control using the external flash device,and is set to 0 when the external flash device has been charged to acertain level which makes it possible to control the slave flash deviceby wireless.

[0174] When the wireless mode setting switch 63 c is in the position toselect the wireless controller mode, only the bit position of the chargecompletion signal which corresponds to the wireless control is set to 0.However, when the wireless mode setting switch 63 c is in the positionto select the wireless master mode, each of the two bit positions of thecharge completion signal which respectively correspond to the wirelesscontrol and the sync mode request is set to 0.

[0175] Table 3 below shows an embodiment of the CF information which istransmitted from the camera body 10 to the external flash device. TABLE3 No. CF INFORMATION CONTENT 10 Photometering Mode TTL, Manual, SettingLight-Magnification, NA 11 Sync Mode Setting Leading Curtain,Successive, Flat Emission, NA 12 Wireless Mode Setting WLset 13 FlashMode Setting Pre-Flash, Flat Emission, Test, Light-Magnification, NA 14Pre-Flash Emission Mode PreM 15 Pre-Flash Emission PreP Intensity 16Pre-Flash Emission PreT Duration 17 Duration of Uniform Tfp FlashEmission 18 Flash Emission Mv1, Mv2 Magnification 19 Maximum Flash DvmaxPhotometering Distance 20 Lens Focal Length 20, 24, 28, 35, 50, 70, 85

[0176] The photometering mode setting has precedence over thephotometering mode request, which is transmitted from the external flashdevice. Namely, even if the manual photometering mode has been set viathe photometering mode request setting switch 63 a on the camera body10, the flash CPU 65 sets the TTL photometering mode if thephotometering mode setting designates the TTL photometering mode.However, the flash CPU 65 sets a photometering mode corresponding to thephotometering mode request if the photometering mode setting designatesan NA mode. The sync mode setting has precedence over the sync moderequest issued by the external flash device because the camera body 10(the CPU 13) determines an appropriate mode to communicate with morethan one external flash device if more than one external flash device isconnected to the camera body 10. Likewise, the wireless mode setting hasprecedence over the wireless mode request issued by the external flashdevice.

[0177] The operation at step S160 for determining the sync mode setting,the pre-flash emission mode PreM and the photometering mode setting willbe hereinafter discussed in detail. Each of the sync mode setting, thepre-flash emission mode PreM and the photometering mode setting isdetermined with reference to Tables 4-1, 4-2 and 4-3 in accordance withthe sync mode request, the charge completion signal, and the presence orabsence of the wireless control for the slave flash device.

[0178] Items of the sync mode request in each of Tables 4-1, 4-2 and 4-3will be hereinafter discussed. In the case of “Presence” in the item“Flash Charge Completion”, a symbol “∘” represents the presence of thecharge completion signal, a symbol “x” represents the absence of thecharge completion signal, and “▪” represents the condition regardless ofthe presence or absence of the charge completion signal.

[0179] Each of the sync mode request and the charge completion signal isinformation which is transmitted from the external flash device to thecamera body 10. On the other hand, each of the sync mode setting, thepre-flash emission mode PreM and the photometering mode setting isinformation which is transmitted from the camera body 10 to the externalflash device. TABLE 4-1 NO WIRELESS CONTROL SYNC MODE REQUEST ChargePhoto- Leading Comple- Sync metering Curtain Suc- Flat tion Mode Mode *1cessive Emission Signal Setting PreM Setting ◯ × ▪ 1 Leading 0 TTLCurtain ◯ ◯ ▪ Suc- 1 TTL cessive × ◯ ▪ Leading 0 TTL Curtain × × ◯ Flat0 Light- Emission Magnifi- or cation or Leading TTL Curtain ◯ and/or ◯and/or ◯ 0 0 NA

[0180] Tables 4-1shows the case where the wireless control for the slaveflash device is not performed. Accordingly, the case where no wirelesscontrol for controlling the slave flash device is performed will behereinafter discussed.

[0181] “Sync Mode Setting” is generally set to designate “LeadingCurtain” (the leading curtain sync flash mode). “Sync Mode Setting” isset to designate “Successive” (the successive sync flash mode) oncondition that no wireless control for controlling the slave flashdevice is performed, that the flash device 50 with “Sync Mode Request”requesting “Leading Curtain” and another flash device 50 with “Sync ModeRequest” requesting “Successive” are connected to the camera body 10,and that these flash devices 50 have been fully charged. However, if“Sync Mode Request” is set to request “Flat Emission” (the flat emissionmode), “Sync Mode Setting” is set to designate “Flat Emission” when theshutter speed of the camera body 10 is equal to or faster than the flashsynchronization speed, or “Sync Mode Setting” is set to designate“Leading Curtain” when the shutter speed of the camera body 10 is slowerthan the flash synchronization speed.

[0182] “Photometering mode setting” is generally set to designate “TTL”(TTL photometering mode). This is because the TTL photometering mode hascharacteristics superior to the object at a long distance, the object ata short distance and the object having a high brightness, as comparedwith “Light-Magnification” (a light-magnification photometering mode).However, if “Sync Mode Request” requests “Flat Emission”, “Photometeringmode setting” is set to designate “Light-Magnification” when the shutterspeed of the camera body 10 is equal to or faster than the flashsynchronization speed, or “Photometering mode setting” is set todesignate “TTL” when that the shutter speed of the camera body 10 isslower than the flash synchronization speed.

[0183] The pre-flash emission mode PreM is determined in accordance withthe sync mode setting. Namely, the pre-flash emission mode PreM is setat 1 only when “Sync Mode Setting” designates “Successive”. Thepre-flash emission mode PreM is 1 when the aforementioned secondpre-flash emission mode has been selected, wherein the flash device 50in which “Sync Mode Request” requests “Leading Curtain” is activated toemit a pre-flash a first time, and subsequently the flash device 50 inwhich “Sync Mode Request” requests “Successive” is activated to emit apre-flash a second time. The pre-flash emission mode PreM is 0 when theaforementioned first pre-flash emission mode, in which all the flashdevices except the built-in flash are driven to emit a pre-flash at thesame time, has been selected.

[0184] Since no flash is discharged in the case of the “Flash ChargeCompletion Signal” being “0”, each of the “Sync Mode Setting” and“Photometering mode setting” is set to “NA”, while the pre-flashemission mode PreM is set to 0. It should be noted that a similarcontrol is also performed for the built-in flash in the item bearing asymbol “*1”. TABLE 4-2 WIRELESS CONTROL Charge Photo- BUILT- SYNC MODEREQUEST Comple- Sync metering IN Leading Suc- Flat tion Mode Mode FLASHCurtain cessive Emission Signal Setting PreM Setting ◯ ▪ ▪ ▪ 1 Leading 0TTL Curtain × ◯ and/or ◯ ▪ Leading 1 Light- Curtain Magnifi- cation × ×× ◯ Flat 1 Light- Emission Magnifi- or cation Leading Curtain ▪ ◯ and/or◯ ▪ 0 Leading 1 NA Curtain ▪ × × ◯ Flat 1 NA Emission or Leading Curtain

[0185] TABLE 4-3 WIRELESS CONTROL Charge Photo- SYNC MODE REQUESTComple- Sync metering Wlint Leading Suc- Flat tion Mode Mode ModeCurtain cessive Emission Signal Setting PreM Setting WLC ▪ ▪ ▪ 1 Leading1 Light- Curtain Magnifi- cation WLFP ▪ ▪ ▪ Flat 1 Light- EmissionMagnifi- or cation Leading Curtain WLM ▪ ▪ ▪ Leading 0 TTL Curtain

[0186] Table 4-2 shows the case where the wireless control forcontrolling the slave flash device is performed with the use of theexternal flash device. Tables 4-3 shows the case where the wirelesscontrol for controlling the slave flash device is performed with the useof the built-in flash in each of the above described three modes of theWLint mode: the WLC mode, the WLFP mode and the WLM mode. In thesecases, “Sync Mode Setting” is generally set to designate “LeadingCurtain”, similar to the case shown in Table 4-1. However, similar tothe case shown in Table 4-1, if “Sync Mode Request” requests “FlatEmission”, “Sync Mode Setting” is set to designate “Flat Emission” whenthe shutter speed of the camera body 10 is equal to or faster than theflash synchronization speed, or “Sync Mode Setting” is set to designate“Leading Curtain ” when the shutter speed of the camera body 10 isslower than the flash synchronization speed.

[0187] “Photometering mode setting” is generally set to designate“Light-Magnification”. However, if the wireless control is performed inthe WLM mode, in which the built-in flash discharges at a shutterrelease, “Photometering mode setting” is set to designate “TTL” since itis hard for the built-in flash to provide a pre-flash emission. Thephotometering mode setting is effective against the external flashdevice connected to the camera body 10. In other words, all the slaveflash devices are controlled solely with “Light-Magnification”.

[0188] The pre-flash emission mode PreM is determined regardless of thesync mode setting in accordance with whether the built-in flash is todischarge for an exposure. Namely, the pre-flash emission mode PreM isset to 0 if the wireless control is performed in the WLM mode, or 1 ifthe wireless control is performed in any other mode (i.e., the WLC modeor the WLFP mode) than the WLM mode.

[0189] As can be understood from the above descriptions, the presentembodiment of the flash photography system is characterized in that theflash photography system has the first pre-flash emission mode, in whichall the flash devices except the built-in flash are driven to emit apre-flash at the same time, and the second pre-flash emission mode, inwhich all the flash devices except the built-in flash are driven to emita pre-flash in a predetermined order. The present embodiment of theflash photography system is further characterized in that the pre-flashemission mode PreM is determined in accordance with the sync modesetting in the case where no wireless control for controlling the slaveflash device is performed, and that the pre-flash emission mode PreM isdetermined in accordance with whether the built-in flash is to dischargefor an exposure in the case where the wireless control for controllingthe slave flash device is performed.

[0190] The pre-flash emission process performed at step S125 will behereinafter discussed in detail with reference to the flow chart shownin FIGS. 12 and 13. The pre-flash emission process is performed to makethe flash device 50 discharge before the main flash emission in order todetermine the light amount of the main flash emission. In the pre-flashemission process, firstly, it is determined whether the WLset flag orthe WLint flag is 1 (step S200). If either the WLset flag or the WLintflag is 1 (if YES at step S200), this indicates that the wirelesscontrol needs to be performed, so that a pre-flash intensity PreP is setto 1, and at the same time, a pre-flash duration PreT is set to 1 (stepS203). Subsequently, control proceeds to step S204.

[0191] If neither the WLset flag nor the WLint flag is 1 (if NO at stepS200), it is determined whether the distance value Dv included the lensinformation read at step S112 exceeds 3 (=2.8 meters), or whether abrightness value Bv determined under available light in the AE processat step S115 exceeds 6 (step S201-1). Each of the distance value Dv andthe brightness value Bv is an APEX value.

[0192] If the distance value Dv exceeds 3 or the brightness value Bvexceeds 6 (if YES at step S201-1), the pre-flash intensity PreP is setto 1 (step S201-2). This is because the brightness of the reflectedlight of a distant object reaching the camera body 10 is generally lowand further because there is a high possibility of the pre-flashemission being interrupted by available light if the object brightnessis high.

[0193] On the other hand, if the distance value Dv does not exceed 3while the brightness value Bv does not exceed 6 (if NO at step S201-1),the pre-flash intensity PreP is set to 1/2 (step S201-3). This is forthe purpose of reducing the power consumption of the external flashdevice by reducing the intensity of the pre-flash because the brightnessof the reflected light of a short-distant object reaching the camerabody 10 is generally high, and further, because there is littlepossibility of the pre-flash emission being interrupted by availablelight even if the object brightness is low.

[0194] Subsequently, it is determined whether the sum of the distancevalue Dv and the f-number AVmin at full aperture is smaller than 8 (stepS202-1). If the sum is smaller than 8 (if YES at step S202-1), thepre-flash duration PreT is set to 1 (step S202-2). If the sum is equalto or greater than 8 (if NO at step S202-1), the pre-flash duration PreTis set to 2 (step S202-3).

[0195] The amount of the received pre-flash is inverse proportional tothe distance value Dv and the f-number AVmin at full aperture.Therefore, a substantial delay in response of the light reception occurssince as the distance value Dv or the f-number Avmin become larger, theamount of the received pre-flash light becomes smaller. Therefore, ifthe sum of the distance value Dv and the f-number AVmin at full apertureis not smaller than 8, the pre-flash duration PreT is set double so thatthe pre-flash can be photometered properly even if such a delay inresponse of the light reception occurs.

[0196] Subsequently, the flash mode setting is set to designate thepre-flash emission mode (step S204), and is transmitted as CFinformation from the camera body 10 to the external flash device via theCF communication (step S205). After the CF communication is performed,it is determined whether the WLint flag is 1 (step S206). If the WLintflag is not 1 (if NO at step S206), the mode-4 communication isperformed to transmit a pulse signal having four successive pulses tothe external flash device (step S207). The external flash device emits apre-flash upon receipt of the pulse signal having four successivepulses. However, if the WLset flag is 1, the external flash device emitstwo successive low flash emissions serving as the aforementionedwireless signal (pre-flash emission command wireless signal) which istransmitted to the slave flash device, and thereafter the external flashdevice emits a pre-flash at substantially the same time as a pre-flashemitted by the slave flash device.

[0197]FIG. 6D shows the waveform of two pre-flash emissions. If thepre-flash emission mode PreM is 0 (the first pre-flash emission mode),all the flash devices except the built-in flash are driven to emit asingle pre-flash at the same time (see the left pulse (1) in FIG. 6D).If the pre-flash emission mode PreM is 1 (the second pre-flash emissionmode), all the flash devices except the built-in flash are driven toemit a pre-flash in a predetermined order so as to emit two pre-flashemissions in total in accordance with the sync mode request set on eachflash device. Two pulses (1) and (2) shown in FIG. 6D represent such twopre-flash emissions (first and second pre-flash emissions). In FIG. 6D,a time “Tint” represents the time interval between the two pre-flashemissions, which is set at 2.5 ms in this particular embodiment.

[0198] On the other hand, if the WLint flag is 1 (if YES at step S206),a timer B is set for the value of the wireless signal interval TW1M fromwhich the value of the time necessary for the mode-4 communication issubtracted, and the timer B is started (step S208). The wireless signalinterval TW1M is a value stored in the RAM 13 a in the flashcommunication process shown in FIG. 11. After the timer B is started, abuilt-in flash low flash emission process is performed (step S209), andsubsequently it is determined whether a timer-B lapsed flag is 1 (stepS210). If the timer-B lapsed flag is not 1 (if NO at step S210) controlrepeats the checking operation at step S210. If the timer-B lapsed flagis 1 (if YES at step S210), control proceeds to step S211. In thebuilt-in flash low flash emission process, the built-in flash isactivated to emit a low flash emission for 30 μs as a wireless signalwhich is transmitted to the slave flash device. The timer-B lapsed flagchanges from 0 to 1 upon the expiration of the timer B.

[0199] If the timer-B lapsed flag is 1 (if YES at step S210) the mode-4communication is performed to make the external flash device startemitting a pre-flash (step S211), and subsequently the built-in flashlow flash emission process is performed again (step S212). Subsequently,control proceeds to step S213-1 shown in FIG. 13.

[0200] The built-in flash low flash emission process is performed twicesuccessively, firstly at step S209 and subsequently at step S212, at thewireless signal interval TW1M, which is stored in the RAM 13 a.Therefore, by performing the mode-4 communication at step S211 upon theexpiration of the timer B, the built-in flash low flash emission processat step S212 and the mode-4 communication at step S211 are completed atsubstantially the same time, and thereafter each of the external flashdevice and the slave flash device emits a pre-flash in synchronizationwith each other.

[0201]FIG. 6E shows the waveform of a wireless signal (the pre-flashemission command wireless signal, a test-flash emission command wirelesssignal or a uniform flash-emission command wireless signal) transmittedto the slave flash device, the waveform of the wireless signal receivedby the slave flash device, and the waveform of the two pre-flashemissions. A wireless signal interval TW1 shown in FIG. 6E representsthe actual interval (measured value) between two successive low flashemissions (wireless signal) received by the light-receiving element 57,which corresponds to the value of the wireless signal interval TW1Mstored in the RAM 13 a.

[0202] In the present embodiment of the flash photography system, thewireless signal interval TW1M varies so as to correspond to the commandprovided by the wireless signal emitted by the built-in flash of thecamera body 10 or the external flash device. The slave flash devicereads the command by reading the wireless signal interval TW1 of the twosuccessive low flash emissions emitted by built-in flash of the camerabody 10 or the external flash device.

[0203] When the wireless signal interval TW1 is 3.2 ms, the pre-flashemission mode PreM is set at 0, and therefore the slave flash device isactivated to emit a pre-flash in the first pre-flash emission mode. Inthis case, all the flash devices except the built-in flash are activatedto emit a single pre-flash at the same time. When the wireless signalinterval TW1 is 4.2 ms, the pre-flash emission mode PreM is set at 1,and therefore the slave flash device is activated to emit a pre-flash inthe second pre-flash emission mode. In this case, the slave flash devicewith the sync mode request having been set to the leading curtain syncflash mode emits a pre-flash in the first place, and another slave flashdevice with the sync mode request having been set to the successive syncflash mode emits a pre-flash in the second place.

[0204] When the wireless signal interval TW1 is 5.2 ms, the sync moderequest is set to the flat emission mode while the pre-flash emissionmode PreM is 1, and therefore the slave flash device is activated toemit a pre-flash in the second pre-flash emission mode. When thewireless signal interval TW1 is 6.2 ms, the flash mode setting is set todesignate a test flash mode while the pre-flash emission mode PreM is 1,and therefore the slave flash device is activated to emit a test flashemission in the second pre-flash emission mode.

[0205] It is determined at step S213-1 whether the WLset flag is 1. Ifthe WLset flag is not 1 (if NO at step S213-1), control skips theoperation at step S213-2, thus proceeding straight from step S213-1 tostep S214. If the WLset flag is 1 (if YES at step S213-1), control waitsa time corresponding to the wireless signal interval TW1M (step S213-2).The waiting operation at step S213-2 is performed for the purpose ofwaiting for the low flash emission of the external flash device (thetransmission of the pre-flash emission command wireless signal by theexternal flash device) to be completed.

[0206] Subsequently, a pre-flash data determination process (“Pre-FlashData Determination Process” shown in FIG. 14) is performed (step S214).In the pre-flash data determination process, two flashlight-emittingmagnifications Mv (Mv1 and Mv2) and two TTL correction values (APEXvalues) Fc (Fc1 and Fc2) are calculated in accordance with the amount ofthe light which is received by the TTL nine-segment photometering sensor22 at a time of a pre-flash emission. After the pre-flash datadetermination process is completed, it is determined whether the syncmode setting designates the successive sync flash mode (step S215).

[0207] If the sync mode setting designates the successive sync flashmode (if YES at step S215), two TTL correction values (APEX values) Fc1and Fc2 and two flashlight-emitting magnifications Mv1 and Mv2 are allreset so that the ratio of the amount of the first pre-flash emission tothe amount of the second pre-flash emission becomes 1/3 to 2/3 (stepS216). More specifically, at step S216 the value of “Fc1−1.58” and thevalue of “Fc2−1.58” are respectively stored as the TTL correction values(APEX values) Fc1 and Fc2 in the RAM 13 a. At the same time, the valueof “Mv1−1.58” and the value of “Mv2−1.58” are respectively stored as theflashlight-emitting magnifications Mv1 and Mv2 in the RAM 13 a.

[0208] If the sync mode setting does not designate the successive syncflash mode (if NO at step S215), it is determined whether apredetermined built-in flash discharge condition is satisfied (stepS215-1). If the predetermined built-in flash discharge condition issatisfied (if YES at step S215-1), the value of “−1.58” and the value of“Mv1−1.58” are respectively stored as the TTL correction value (APEXvalue) Fc1 and the flashlight-emitting magnification Mv1, so that theratio of the amount of the main flash emission of the built-in flash tothe amount of the main flash emission of the slave flash device becomes1/3 to 2/3 (step S215-2).

[0209] Subsequently, the flash mode setting is set to designate alight-magnification flash mode (step S217), and is transmitted as CFinformation from the camera body 10 to the external flash device via theCF communication (step S218). After the CF communication is performed,it is determined whether the WLint flag is 1 (step S219). If the WLintflag is 1 (if YES at step S219), the wireless signal interval TW1M and awireless signal interval TW2M are calculated from the followingequations:

TW 1 M=2 ms+(Mv 1+5)×128/1000 (ms)

[0210] and

TW 2 M=2 ms+(Mv 2+5)×128/1000 (ms);

[0211] and are written over the previous wireless signal interval TW1Mand the previous wireless signal interval TW2M, respectively, in the RAM13 a (step S220).

[0212] Subsequently, it is determined whether the PreM is 0 (stepS221-1). If the PreM is 0 (if YES at step S221-1), the built-in flash isactivated to emit a low flash emission twice successively at thewireless signal interval TW1M stored in the RAM 13 a to emit a lightsignal as a light-magnification command wireless signal (step S221-2),and subsequently control returns to the camera main process. Uponreceipt of the light-magnification command wireless signal, the slaveflash device sets the flashlight-emitting magnification Mv at theflashlight-emitting magnification Mv1.

[0213] On the other hand, if the PreM is 1 (if NO at step S221-1), thebuilt-in flash is activated to emit a low flash emission three timessuccessively to emit a light signal as a light-magnification commandwireless signal in such a manner that the first interval between thefirst two low flash emissions becomes identical to the wireless signalinterval TW1M stored in the RAM 13 a and that the latter intervalbetween the latter two low flash emissions become identical to thewireless signal interval TW2M stored in the RAM 13 a (step S221-3), andsubsequently control returns to the camera main process. Thelight-magnification command wireless signal includes the data of theflashlight-emitting magnifications Mv1 and Mv2. The slave flash devicesets the flashlight-emitting magnification Mv in accordance with the setsync mode request. Namely, the slave flash device with the sync moderequest requesting the leading curtain sync flash mode sets theflashlight-emitting magnification Mv at the flashlight-emittingmagnification Mv1, while the slave flash device with the sync moderequest requesting the successive sync flash mode sets theflashlight-emitting magnification Mv at the flashlight-emittingmagnification Mv2.

[0214]FIG. 6F shows the waveform of the light-magnification commandwireless signal transmitted to the slave flash device, and the waveformof the light-magnification wireless signal received by the slave flashdevice. Two wireless signal intervals TW1 and TW2 shown in FIG. 6Frepresent the actual intervals (measured values), which correspond tothe values of the two wireless signal intervals TW1M and TW2M stored inthe RAM 13 a, respectively.

[0215] If the WLint flag is not 1 (if NO at step S219), it is determinedwhether the WLset flag is 1 (step S222). If the WLset flag is not 1 (ifNO at step S222), control returns to the camera main process. If theWLset flag is 1 (if YES at step S222), the mode-4 communication isperformed to make the external flash device emit a low flash emission toemit a light signal as light-magnification command wireless signal (stepS223), and subsequently control returns to the camera main process.

[0216] [Pre-Flash Data Determination Process]

[0217] The pre-flash data determination process performed at step S214will be hereinafter discussed in detail with reference to the flow chartshown in FIG. 14. In this process, firstly a variable m is set to 1(step S250) and subsequently a pre-A/D conversion process (“Pre-A/DConversion Process” shown in FIG. 15) is performed (step S251). In thepre-A/D conversion process, the output voltage corresponding to thephotocurrent of each zone sensor 22_n (n=1˜9) of the nine-segmentphotometering sensor 22 is converted from analogue to digital more thanone time successively, and this successive converting operation isrepeated a predetermined number of cycles.

[0218] After the pre-A/D conversion process is performed, it isdetermined whether the pre-flash intensity PreP is 1/2 (step S252). Ifthe pre-flash intensity PreP is 1/2 (if YES at step S252), the pre-A/Dconverted data Ad(m) is replaced with the pre-A/D converted data Ad (m)obtained in the pre-A/D conversion process at step S251 to which 1 (one)is added, and is stored in the RAM 13 a (step S253), wherein “m”represents the aforementioned variable (m=1˜9).

[0219] The operation at step S253 is performed for the purpose ofcompensating for the A/D converted data Ad(m) obtained when thepre-flash intensity PreP is 1/2, which is smaller than that obtainedwhen pre-flash intensity PreP is 1 by 1EV. If the pre-flash intensityPreP is not 1/2 (if NO at step S252), control proceeds straight fromstep S252 to step S254.

[0220] It is determined at step S254 whether the pre-flash intensityPreP is 1. If the pre-flash intensity PreP is not 1 (if NO at stepS254), control proceeds to step S259. If the pre-flash intensity PreP is1 (if YES at step S254), the variable m is set to 11 (step S255), andthe pre-A/D conversion process is performed (step S256). The operationsat step S255 and S256 are performed to obtain pre-flash data at thesecond pre-flash emission. Subsequently, it is determined whether thepre-flash intensity PreP is 1/2 (step S257). If the pre-flash intensityPreP is 1/2. (if YES at step S257), the pre-A/D converted data Ad(m) isreplaced with the pre-A/D converted data Ad(m) to which 1 (one) isadded, and is stored in RAM 13 a (step S258), wherein “m” represents theaforementioned variable (m=11˜19). If the pre-flash intensity PreP isnot 1/2 (if NO at step S257), control proceeds straight from step S257to step S259.

[0221] Subsequently, the variable m is set to 21 (step S259) and thepre-A/D conversion process is performed (step S260). The operations atstep S259 and S260 are performed to obtain A/D conversion data in astate with no flash emission, i.e., only with available light.Subsequently, at step S261 a first pre-flash brightness Bvp(m) iscalculated and stored in RAM 13 a for each of the nine different zonesensors 22_1 through 22_9 of the TTL nine-segment photometering sensor22 via the following equation:

Bvp(m)=ln(2^(Ad(m))−2^(Ad(m−20)))/ln2

[0222] wherein “m” represents the aforementioned variable (m=1˜9).

[0223] Namely, in the operation at step S261, a photocurrent which isgenerated solely the first pre-emission is calculated by subtracting aphotocurrent generated only by available light from a photocurrentgenerated by both the first pre-flash emission and available light, andthe value of the calculated photocurrent is logarithmic-compressed againto obtain the first pre-flash brightness Bvp(m) due to only the firstpre-flash emission.

[0224] Subsequently, a flash emission amount calculation process (“FlashEmission Amount Calculation Process” shown in FIG. 16) is performedusing the pre-flash brightness Bvp(m) (step S262), and subsequently thecalculated flashlight-emitting magnification Mv and the calculated TTLcorrection value (APEX value) Fc are stored as Mv1 and Fc1 in the RAM 13a (step S263). Subsequently it is determined whether the pre-flashintensity PreP is 1 (step S264). If the pre-flash intensity PreP is not1 (if NO at step S264), control returns to the camera main process. Ifthe pre-flash intensity PreP is 1 (if YES at step S264), at step S265 asecond pre-flash brightness Bvp(m) is calculated and stored in the RAM13 a for each of the nine different zone sensors 22_1 through 22_9 ofthe TTL nine-segment photometering sensor 22 via the following equation:

Bvp(m)=ln(2^(Ad(m+10))−2^(Ad(m+20)/) ln 2

[0225] wherein “m” represents the aforementioned variable (m=1˜9).

[0226] In the operation at step S265, the second pre-flash brightnessBvp(m) (wherein m=1˜9) is determined in accordance with the pre-A/Dconverted.data Ad(11)˜Ad(19) obtained in the second pre-A/D conversionprocess. Subsequently, the flash emission amount calculation process isperformed using the second pre-flash brightness Bvp(m) obtained at stepS265 (step S266). Subsequently, the calculated flashlight-emittingmagnifications Mv and the calculated TTL correction value (APEX value)Fc are stored as Mv2 and Fc2 in the RAM 13 a (step S267). Subsequently,control returns to the camera main process.

[0227] [Pre-A/D Conversion Process]

[0228] The pre-A/D conversion process performed at steps S251, S256 andS260 will be hereinafter discussed in detail with reference to the flowchart shown in FIG. 15. In this process, firstly, the timer A set for2.5 ms is started (step S300), and subsequently control waits 50 μs forthe pre-emission to be stable (step S301). Subsequently, a number of A/Dconversions “Time” is set to the value corresponding to the pre-flashduration PreT multiplied by 12 (step S302). At step S303, a variable nis set to 0, a variable k is set to 1, and each of the first throughfour ports Pk1 through Pk4 of the group of ports Pk is set to “0” tooutput a signal of “0”. The first through four ports Pk1 through Pk4 ofthe group of ports Pk are connected to the selector 102 of the TTLphotometering circuit 19. In a state where the output signals of thefirst through four ports Pk1 through Pk4 are all “0”, the first zonesensor 22_1 of the nine-segment photometering sensor 22 is selected bythe selector 102, and an output voltage corresponding to thephotocurrent output from the first zone sensor 22_1 is output to the A/Dconversion port Pk5 of the CPU 13 (see FIG. 2).

[0229] Subsequently, the timer-B lapsed flag is set to 0 (step S304),the timer B set for 33 μs is started (step S305), and it is determinedwhether the variable n is less than 9 (step S306) If the variable n isless than 9 (if YES at step S306) the input voltage of the A/Dconversion port Pk5 is converted from analogue to digital four timessuccessively, and these four A/D converted values are stored in fouraddresses A(m+n, k), A(m+n, k+1), A(m+n, k+2) and A(m+n, k+3)respectively (step S309). The variable m at step S309 corresponds to thevariable m at step S250, S255 or S259 in the pre-flash datadetermination process shown in FIG. 14.

[0230] After the operation at step S309, the variable n is incrementedby one (step S310). Subsequently, a four-bit signal corresponding to thevariable n is output to the first through four ports Pk1 through Pk4 toselect the zone sensor 22_(n+1) of the nine-segment photometering sensor22 (step S311). Subsequently, it is determined whether the timer-Blapsed flag is 1 (step S312). Control repeats the operation at step S312until the timer-B lapsed flag becomes 1. If the timer-B lapsed flag is 1(if YES at step S312), control returns to the operation at step S304,and thereafter the operations at steps S304, S305, S306, S309, S310,S311 and S312 are repeated until it is determined at step S306 that thevariable n is not less than 9. Accordingly, the A/D conversion, which iscarried out four times, of the output voltage corresponding to thephotocurrent of each of the nine zone sensors 22_1 through 22_9 of thenine-segment photometering sensor 22 is carried out (i.e., is carriedout nine times), switching from one zone sensor to a subsequent zonesensor at an interval of 33 μs, to thereby constitute one A/D conversioncycle, wherein the nine sets of four A/D converted values are stored inthe RAM 13 a.

[0231] If it is determined at step S306 that the variable n is not lessthan 9, four is added to the variable k, while the variable n is set to0 (step S307). This signifies an end of one A/D conversion cycle.Subsequently, it is determined whether the variable k is equal to orgreater than the number of A/D conversions ‘Time’ set at step S302 (stepS308). If the variable k is not equal to or greater than the number ofA/D conversions ‘Time’ (if NO at step S308), control proceeds to stepS309 to perform the operations at steps S309 through S312 and step S304through 308. Namely, another A/D conversion cycle is carried out. If thepre-flash duration PreT is 1, three A/D conversion cycles are carriedout. Therefore, twelve A/D converted values (data) of each zone sensor22_n are obtained. The processing time for this A/D conversion from stepS302 through step S314 is approximately 900 μs, and the operations fromstep S301 through step S314 is completed before the lapse of 50 μs ofthe pre-flash duration PreT (1 ms). On the other hand, if the pre-flashduration PreT is 2, six of the A/D conversion cycles are carried out. Inthis case, twenty four A/D converted values (data) of each zone sensor22_n are obtained.

[0232] If the variable k is equal to or greater than the number of A/Dconversions ‘Time’ (if YES at step S308), the maximum valuecorresponding to the maximum intensity is selected from among the A/Dconverted values stored in the addresses A(m+n, k) for each variable n(=0˜8), and the selected maximum value for each variable n (=0˜8) isstored in a corresponding address A(m+n)max (step S313). Subsequently,at step S314, an average value of the A/D converted values among the A/Dconverted values stored in the addresses A(m+n, k) whose difference fromthe corresponding maximum value selected and stored in the addressesA(m+n)max at step S313 is within 1EV is determined for each zone sensor22_(n+1) (n=0˜8), and is stored in the RAM 13 a as the pre-A/D converteddata Ad(m+n) (n=0˜8). The reason why the A/D converted values among theA/D converted values stored in the addresses A(m+n, k) whose differencefrom the corresponding maximum value selected and stored in theaddresses A(m+n) max at step S313 is equal to or smaller than 1EV areremoved is that the amount of the reflected light of the object reachingthe camera is small, to thereby cause a substantial delay in response ofthe light reception if the sum of the distance value Dv and the f-numberAVmin at full aperture is greater than a predetermined value, i.e., thatprecise A/D converted data cannot be obtained due to such a substantialdelay.

[0233] Subsequently, it is determined whether the timer-A lapsed flag is1 (step S315). Control repeats the checking operation at step S315 untilthe timer-A lapsed flag becomes 1. If the timer-A lapsed flag is 1 (ifYES at step S315), control returns to the pre-flash data determinationprocess shown in FIG. 14. It takes precisely 2.5 ms for the pre-A/Dconversion process described above to be completed.

[0234]FIG. 31 shows an enlarged schematic view of a part of the waveformof the voltage PDfl shown in FIG. 7, which corresponds to the output ofthe light-receiving element 85. The ripple frequency of the waveform ofthe voltage PDfl is approximately 20 μs to 40 μs. In the above describedpre-A/D conversion process, the processing time for the operation atstep S309 in which the output voltage corresponding to the photocurrentof each zone sensor 22_n of the nine-segment photometering sensor 22 isconverted from analogue to digital four times successively isapproximately 16 μs since the processing time for each of the four A/Dconversions at step S309 is approximately 4 μs. This processing time ofapproximately 16 μs substantially corresponds to a half period of theripple frequency of the waveform of the pre-flash emission. Therefore,there is a high possibility of the A/D conversion operation at step S309being performed for a half period of the ripple frequency of thewaveform of the pre-flash emission which that includes a peak and abottom thereof. This makes it possible to obtain precise values in theA/D conversion operation. Due to such reasons, an A/D conversion isperformed four times successively in the A/D conversion operation atstep S309. In FIG. 31, ‘Ts’ represents a time for the output of eachzone sensor 22_n of the nine-segment photometering sensor 22 to bestable. In the present embodiment of the flash photography system, sincethe switching interval is 33 μs and the processing time for the four A/Dconversions is 16 μs, ‘Ts’ is 17 μs.

[0235] [Flash Emission Amount Calculation Process]

[0236] The flash emission amount calculation process performed at stepsS262 and S266 will be hereinafter discussed in detail with reference tothe flow chart shown in FIG. 16. In this process, firstly it isdetermined whether the distance value Dv is available (step S350). Thedistance value Dv is input at step S112 in the camera-lens communicationprocess in the case where an interchangeable lens which can havecommunication with the camera body 10 via the camera-lens communicationinterface 7 is mounted to the camera body 10. Therefore, if it isdetermined that the distance value Dv is not available, the CPU 13determines that the currently-mounted interchangeable lens is aconventional type which cannot have communication with the CPU 13 of thecamera body 10. The distance value Dv is an APEX value.

[0237] If the distance value Dv is available (if YES at step S350), itis determined whether the Bounce flag is 1 (step S351). The Bounce flagis set at 1 when a head of the external flash device is tilted orswiveled upward to give bounced light to the object. If the Bounce flagis not 1 (if NO at step S351), it is determined whether either the WLsetflag or the WLint flag is 1 (step S352). If neither the WLset flag northe WLint flag is 1 (if NO at step S352), namely, if wireless control isnot performed, it is determined whether the distance value Dv is smallerthan −1 (=0.7 meters) (step S353).

[0238] If the distance value Dv is available (if YES at step S350), orif the Bounce flag is not 1 (if NO at step S351), of if a wirelesscontrol is not performed (if No at step S352) and the distance value Dvis not smaller than −1 (if NO at step S353), a reference pre-flashbrightness value Bvpc when a pre-flash emission is projected toward anobject having a reference reflectivity is determined at step S354 usingthe following equation:

Bvpc=Ks−Avmin−Dv

[0239] wherein “Avmin” represents the f-number at full aperture, and“Ks” represents the constant determined from the following equation:

Ks=Bvps+Dvs

[0240] wherein “Dvs” represents the reference distance value accordingto the APEX system, and “Bvps” represents the brightness value when apre-flash emission is projected toward an object having a referencereflectivity which is located at the reference distance value Dvs, inthe case where the pre-flash intensity PreP is set at 1. “Bvps-Avmin”represents the pre-flash brightness value photometered via thenine-segment photometering sensor 22 when the object brightness at apre-flash is the aforementioned reference pre-flash brightness valueBvps.

[0241] If the distance value Dv is not available (if NO at step S350),or if the Bounce flag is 1 (if YES at step S351), or if a wirelesscontrol is performed (if YES at step S352), or if the distance value Dvis smaller than −1 (if YES at step S353), the reference pre-flashbrightness value Bvpc is calculated without using the distance value Dv(steps S355 and S356). This is because there are some conditions (e.g.,a condition wherein a head of the external flash device is tilted orswiveled upward to produce bounced flash, or wherein a wireless controlis performed, or wherein the object is located behind the minimumdistance in the illumination range of the flash system, etc.) which donot agree with the relationship between the distance value Dv and thepre-flash emission.

[0242] In the operation at step S355, a maximum pre-flash brightnessBvp(m)max is selected from among the nine pre-flash brightness valuesBvp(m) obtained via the nine different zone sensors 22_1 through 22_9 ofthe TTL nine-segment photometering sensor 22 (the variable m=1˜9), andthe identification number or numbers of one or more zone sensors of theTTL nine-segment photometering sensor 22 whose difference in brightnessvalue from the maximum pre-flash brightness Bvp (m) max is smaller than5EV are stored in a register X in the CPU 13. The brightness value 5EVwhich determines the range of the difference in brightness value fromthe maximum pre-flash brightness Bvp(m)max corresponds to the latitudeof a typical negative film. Such a brightness value can be suitablyadjusted to, e.g. 3EV, according to the film type in use. The reason whyone or more zone sensors of the TTL nine-segment photometering sensor22, whose difference in brightness value from the maximum pre-flashbrightness Bvp(m)max is equal to or greater than 5EV, are removed isthat the object positioned to correspond to one zone sensor at whichsuch a pre-flash brightness is obtained is located far away from theobject corresponding to the maximum pre-flash brightness Bvp(m)max andis therefore considered to have little influenced by flash lightemission.

[0243] Subsequently, in the operation at step S356, a minimum pre-flashbrightness Bvp(m)min is selected from among pre-flash brightness valueor values Bvp (x) obtained via one or more zone sensors of the number ornumbers selected at step S355, and the reference pre-flash brightnessvalue Bvpc is calculated at step S356 using the following equation:

Bvpc=(Bvp(x)max+Bvp(x)min)/2.

[0244] Each of the maximum pre-flash brightness Bvp(m)max and theminimum pre-flash brightness Bvp(m)min is within the latitude of film inuse due to the operation at step S355. If the minimum pre-flashbrightness Bvp(m)min is not obtained at step S356, the referencepre-flash brightness value Bvpc is regarded to be equal to the maximumpre-flash brightness Bvp(m)max.

[0245] After the reference pre-flash brightness value Bvpc has beendetermined, the identification number or numbers of one or more zonesensors of the TTL nine-segment photometering sensor 22 whose differencein brightness value from the reference pre-flash brightness value Bvpcis greater than −2EV and smaller than +2EV are stored in a register Y inthe CPU 13 (step S357). This operation at step S357 is performed for thepurpose of removing the object having an excessively high reflectivityor located behind the minimum distance in the illumination range of theflash system, or the object having an excessively low reflectivity orlocated far away from the maximum distance in the illumination range ofthe flash system.

[0246] Subsequently, it is determined whether a number has beenregistered in the register Y (step S358). If one or more numbers havebeen registered in the register Y (if YES at step S358), the averagevalue of pre-flash brightness values Bvp(y) obtained via those zonesensors of the TTL nine-segment photometering sensor 22 whose numbershave been registered in the register Y is calculated, and is stored inthe RAM 13 a as a calculated pre-flash brightness value (an averagepre-flash brightness value) Bvptyp (step S359). If no number has beenregistered in the register Y (if NO at step S358), the referencepre-flash brightness value Bvpc is stored in the RAM 13 a as thecalculated pre-flash brightness value (an average pre-flash brightnessvalue) Bvptyp (step S360).

[0247] The flashlight-emitting magnification Mv is calculated at stepS361 via the following equation:

Mv=Tv+Av+Avc−Sv−Bvptyp−Avmin

[0248] wherein “Tv” represents the optimum time value (optimum shutterspeed) according to the APEX system (however, Tv is regarded to be equalto Tvx if the time value Tv is smaller than the flash sync speed); “Av”represents the aperture value according to the APEX system; “Avc”represents the photometering correction information; and “Sv” representsthe film speed value according to the APEX system.

[0249] After the flashlight-emitting magnification Mv has beencalculated, a TTL correction calculation is performed (steps S362 toS365). In this calculation, firstly ratio data D(n) is calculated atstep S362 using the following equation:

D(n)=2^((Bvp(n)-Bvptyp)).

[0250] The ratio data D(n) shows how many times the pre-flash brightnessvalue Evp(n) at a photometering zone n (n=1˜9) of the TTL nine-segmentphotometering sensor 22 is greater than the calculated pre-flashbrightness value Bvptyp.

[0251] Subsequently, the ratio data D(n) is substituted into thefollowing equation (1) to determine an estimated receiving light amount(a relative output) F that the TTL direct photometering sensor 23receives from the pre-flash brightness value Bvp(n) at each zone sensor22_(n) of the TTL nine-segment photometering sensor 22 (step S363)Subsequently, the ratio data D(n) of the photometering zone n which hasnot been stored in the register Y is reset to 1 (a specified value), andall the ratio data D(n) are substituted into the following equation (1)to determine a reference receiving light amount Ftyp (step S364).

F=36×D(5)+12×(D(2)+D(4)+D(6)+D(8))+4×(D(1)+D(3)+D(7)+D(9))  (1)

[0252] Subsequently, the ratio of the estimated receiving light amount Fto the reference receiving light amount Ftyp is regarded as a TTLcorrection value (APEX value) Fc, and accordingly the TTL correctionvalue (APEX value) Fc is calculated at step S365 using the followingequation:

Fc=ln(F/Fype)/ln 2

[0253] Subsequently, control returns to the pre-flash data determinationprocess shown in FIG. 14.

[0254] The coefficient of the ratio data D(n) at each photometering zonen in the above equation (1) is referred herein to as a weighting factor.

[0255] The weighting factors, which are respectively assigned to thenine different zone sensors 22_1 through 22_9 of the TTL nine-segmentphotometering sensor 22, are determined in accordance with thedistribution sensitivity of the TTL direct photometering sensor 23.

[0256]FIG. 8B is a graph showing the distribution of the light receivedby the TTL direct photometering sensor 23 in the horizontal directionacross the center of the TTL nine-segment photometering sensor 22. InFIG. 8B, the vertical axis represents the amount of the light receivedby the TTL direct photometering sensor 23, while the horizontal axiscorresponds to the horizontally-aligned fourth, fifth and sixthphotometering zones 4, 5 and 6 of the TTL nine-segment photometeringsensor 22 shown in FIG. 8A. The distribution of the light received bythe TTL direct photometering sensor 23 in the horizontal directionacross the center of the TTL nine segment photometering sensor 22 isregarded to be identical to that in the vertical direction across thecenter of the TTL nine-segment photometering sensor 22. Namely, the samedistribution as that shown in FIG. 8B can be obtained if the horizontalaxis of FIG. 8B is made to correspond to the vertically-aligned second,fifth and eighth photometering zones 2, 5 and 8 of the TTL nine-segmentphotometering sensor 22 shown in FIG. 8A.

[0257]FIG. 8C is a diagram showing the amount of the light received bythe TTL direct photometering sensor 23 via each of the nine differentphotometering zones 1 through 9 as a percentage (%) relative to thetotal amount of the light received by the TTL direct photometeringsensor 23. In the present embodiment of the flash photography system,the percentage represents the aforementioned weighting factor. Namely,36% of the sensitivity is given to the output of the zone sensor 22_5 ofthe TTL nine-segment photometering sensor 22, 12% of the sensitivity isgiven to the output of each of the zone sensors 22_2, 22_4, 22_6 and22_8 of the TTL nine-segment photometering sensor 22, and 4% of thesensitivity is given to the output of each of the zone sensors 22_1,22_3, 22_7 and 22_9 of the TTL nine-segment photometering sensor 22. Thefunction for determining the aforementioned relative output F of the TTLdirect photometering sensor 23 is expressed by the above equation (1).

[0258] A specific example of the flash emission amount calculationprocess shown in FIG. 16 will be hereinafter discussed. FIG. 9A shows acase where the main object is located to correspond to only a centralpart (which includes the fifth and eighth photometering zones 5 and 8)of the TTL nine-segment photometering sensor 22 while the background islocated far away from the object. FIG. 9B is a diagram showing thebrightness determined with the TTL nine-segment photometering sensor 22at each of the nine different photometering zones 1 through 9 thereof,in the particular case shown in FIG. 9A at the pre-flash emission,wherein the values shown in FIG. 9B are reference pre-flash brightnessvalues Bvpc. In this particular case shown in FIGS. 9A and 9B, if theobject brightness is photometered via the TTL direct photometeringsensor 23 and if exposure control is carried out simply by using theoutput of the TTL direct photometering sensor 23, the main object willbe overexposed since the reflected light from the periphery of theobject is little.

[0259]FIG. 9C shows a case where the main object is located tocorrespond to a major part (which includes the first, second, fourth,fifth, seventh and eighth photometering zones 1, 4, 5, 7 and 8) of theTTL nine-segment photometering sensor 22 while an object having a highreflectivity such as a mirror or the like exits in the background (whichincludes the third, fourth and fifth photometering zones 3, 6 and 9) ofthe main object. FIG. 9D is a diagram showing the brightness (i.e., thereference pre-flash brightness values Bvpc) determined with the TTLnine-segment photometering sensor 22 at each of the nine differentphotometering zones thereof, for the particular case shown in FIG. 9C atthe pre-flash emission. In this particular case shown in FIGS. 9C and9D, if the object brightness is photometered via the TTL directphotometering sensor 23 and if exposure control is carried out simply byusing the output of the TTL direct photometering sensor 23, the mainobject will be underexposed since the reflected light from the peripheryof the object is excessively great.

[0260] If the flash emission amount calculation process shown in FIG. 16is performed on condition shown in FIG. 9A or 9C, the results shown inTable 5 below are obtained. However, such results are obtained on thefollowing condition:

Ks=12, Avmin=4, Dv=4, Tv=7, Av=6, Avc=0,

[0261] and

Sv−5.

[0262] TABLE 5 Bvpty Bvpc Y p Mv F Ftyp Fc 4 5, 8 3.5 0.5 68.6 111.4−0.70 4 1, 2, 4, 5, 7, 8 4 0 240 100 1.25

[0263] As can be understood from the results shown in Table 5, theexposure compensation has underexposed the main object by 0.7EV in thecase shown in FIG. 9A, and that the exposure compensation hasoverexposed the main object by 1.26EV in the case shown in FIG. 9C.Accordingly, correct exposure can be attained even if an object having ahigh reflectivity such as a mirror, or the like exits, in the vicinityof the main object, or even if the main object is relatively small withrespect to the background.

[0264] [The Exposure Process]

[0265] The exposure process performed at step S128 in the camera mainprocess will be hereinafter discussed in detail with reference to theflow chart shown FIGS. 17 and 18. In the exposure process, firstly, theoutput ports Pm2 and Pm3 are set to “0” and “1”, respectively (stepS400). Due to this operation at step S400, the MOS_SW 200 is switched ONto thereby cause the integrating capacitor 201 to discharge in the TTLdirect photometering circuit 20 (see FIG. 3). In this state, theterminal Q of the terminal connector 4 is in a communication availablestate since the transistor 206 is OFF. The operation at step S400 isalso performed in the CPU's port initialization operation at step S100.

[0266] Subsequently, the timer B is set for an exposure time 1/2^(Tv)(step S401), and it is determined whether the sync mode settingdesignates the flat emission mode (step S402).

[0267] The cases where the sync mode setting designates a mode otherthan the flat emission mode, the flash device 50 discharges to emit themain flash emission in the normal flash emission mode, i.e., not in theflat emission mode.

[0268] If the sync mode setting does not designate the flat emissionmode (if NO at step S402), the timer B is started in order to cause theleading curtain to start moving (step S403). Subsequently, mode-3communication is performed (step S404). In the mode-3 communication, apulse signal having three successive pulses is output to the externalflash device. Upon receipt of the pulse signal having three successivepluses, the external flash device prepares for the main flash dischargein the normal mode. FIG. 6A shows the signals input to the terminals C,R, Q and X of the terminal connector 56 and for a flash emission whenthe sync mode setting designates the leading curtain sync flash mode.FIG. 6B shows the signals input to the terminals C, R, Q and X of theterminal connector 56 and for flash emissions when the sync mode settingdesignates the successive sync flash mode.

[0269] After the mode-3 communication is performed, it is determinedwhether the timer-B lapsed flag is 1 (step S405) If the timer-B lapsedflag is not 1 (if NO at step S405), control repeats the checkingoperation at step S405. If the timer-B lapsed flag is 1 (if YES at stepS405), it is determined whether the WLint flag is 1 (step S425). If theWLint flag is not 1 (if NO at step S425), control skips the operationsof steps S426 and S427, and proceeds straight from step S425 to stepS428. If the WLint flag is 1 (if YES at step S425), the built-in flashis activated to emit a single low flash to transmit a wireless signalserving as the main-flash emission command wireless signal to the slaveflash device (step S426). Subsequently, control waits 3 ms (step S427).Subsequently, control proceeds to step S428. Upon receipt of themain-flash emission command wireless signal, the slave flash devicestarts emitting the main flash with the set flashlight-emittingmagnification Mv.

[0270] Subsequently, it is determined whether the photometering modesetting designates the TTL photometering mode (step S428). In thepresent embodiment of the flash photography system, the built-in flashis activated to discharge for the main exposure if a predeterminedbuilt-in flash discharge condition is satisfied (step S430-1) oncondition that the sync mode setting designates a mode other than theflat emission mode and that the photometering mode setting designatesthe TTL photometering mode. The predetermined built-in flash dischargecondition is that the built-in flash has been popped up and also fullycharged.

[0271] If the photometering mode setting does not designate the TTLphotometering mode (if NO at step S428), the terminal X is set to “0”(step S436). Immediately after the terminal X becomes “0”, the externalflash device starts discharging (see FIG. 6A). In this case, theexternal flash device is in one of the following flash modes: thelight-magnification flash mode (see step S217), an auto flash mode, or amanual flash mode, which has been determined via information which hasbeen previously transmitted (either by hard connection or by wirelesscontrol). After the terminal X is set to “0” at step S436, control waits1 ms (step S437) and subsequently the trailing curtain is released tostart moving (step S438). Subsequently, the ports Pm2 and Pm3 areinitialized (step S439), and control returns to the camera main process.

[0272] If the photometering mode setting designates the TTLphotometering mode (if YES at step S428), a voltage value correspondingto D/A data T_ttl(Sv-Fc1) is read out from a D/A data table T_ttl (x) tobe output to the D/A conversion port Pm1 of the group of ports Pm of theCPU 13, the output port Pm3 is set to “0”, and the port Pm2 is set toserve as an input port (step S429). The above-mentioned D/A data tableT_ttl(x) corresponds to an APEX value x. Furthermore, the D/A data T_ttl(Sv-Fc1) corresponds to D/A data at the time the APEX value x is equalto the sum of the film speed value Sv and the TTL correction value Fc1.Subsequently, the terminal X is set to “0” to thereby cause the externalflash device to discharge (step S430) and it is determined whether theaforementioned predetermined built-in flash discharge condition issatisfied (step S430-1). If the predetermined built-in flash dischargecondition is satisfied (if YES at step S430-1), the xenon flashtube 21is also activated to discharge via the built-in flash circuit 14 (stepS430-2). If the predetermined built-in flash discharge condition is notsatisfied (if NO at step S430-1), control skips step S430-2 and advancesto step S431.

[0273] Setting the output port Pm3 to “0” at step S429 causes the MOS_SW200 of the TTL direct photometering circuit 20 to be switched OFF. Inthis state, since the flash has not yet discharged, the output of theoperational amplifier 202 is “0” while the output of the comparator 203is also “0”. Thereafter, if the external flash device and the built-inflash discharge at steps S430 and S430-2, respectively, the TTL directphotometering sensor 23 receives light (object light) reflected by filmsurface to output a photocurrent corresponding to the amount of thereceived light. The integrating capacitor 201 integrates (accumulates)this photocurrent. As a result, the output voltage of the operationalamplifier 202 rises. Thereafter, if the output voltage of theoperational amplifier 202 reaches the output voltage corresponding tothe D/A data T_ttl(Sv-Fc1) of the D/A conversion port Pm1, the output ofthe comparator 203 changes to “0” to “1”. This causes the output of thetransistor 206 to change from low to high, thus causing the terminal Qto change from “0” to “1” to quench the discharge of each of theexternal flash device and the built-in flash.

[0274] It is determined at step S431 whether the sync mode settingdesignates the successive sync flash mode. In a state where the syncmode setting designates the successive sync flash mode, wireless controlis not performed, more than one external flash device is connected tothe camera body 10, and the sync mode requests from the external flashdevices are not all the same; some of them request the leading curtainsync flash mode and others the successive sync flash mode. If the syncmode setting designates the successive sync flash mode (if YES at stepS431), the flash device(s) with the sync mode request requesting theleading curtain sync flash mode discharges a first time, while anotherflash device(s) with the sync mode request requesting the successivesync flash mode discharges a second time. The amount of the first flashdischarge (see the waveform of a first flash emission (1) in FIG. 6B)and the amount of the second flash discharge (see the waveform of asecond flash emission (2) in FIG. 6B) are controlled so as to have theratio of (1/3) to (2/3). It should be noted that the built-in flash isactivated to discharge simultaneously with the first flash emission ofthe external flash device whose sync mode request requests the leadingcurtain sync flash mode.

[0275] If the sync mode setting designates the successive sync flashmode (if YES at step S431), control waits 3 ms (step S432). Upon thelapse of 3 ms, the output port Pm2 is set to “1”, the output port Pm3 isset to “1”, and a voltage corresponding to a D/A data T_ttl (Sv-Fc2) isread out from the D/A data table T_ttl(x) to be output to the D/Aconversion port Pm1 (step S433). The D/A data T_ttl (Sv-Fc2) correspondsto D/A data at the time the APEX value x is equal to the sum of the filmspeed value Sv and the TTL correction value Fc2. Subsequently, controlwaits 0.5 ms with the terminal Q remaining at “1” (step S434). Theoperation at step S434 is performed to make preparations for the secondflash emission. Upon the lapse of 0.5 ms, the output port Pm3 is set to“0”, and the port Pm2 is set to serve as an input port (step S435). Thissets the terminal X to “0” to thereby cause the external flash device todischarge to emit the second flash emission. Immediately after theoutput voltage of the operational amplifier 202 reaches the outputvoltage T_ttl(Sv-Fc2) of the D/A conversion port Pm1 due to the secondflash emission, the terminal Q changes from “0” to “1” to quench thedischarge of each of the external flash device and the built-in flash.After the operation at step S435, control waits 1 ms (step S437) andsubsequently the trailing curtain of the focal plane shutter is releasedto start moving (step S438). Subsequently, the ports Pm2 and Pm3 areinitialized (step S439), and control returns to the camera main process.

[0276] If the sync mode setting does not designate the successive syncflash mode (if No at step S431), control proceeds from step S431 to stepS437, so that the second flash discharge is not performed. Thereafter,control waits 1 ms (step S437) and subsequently the trailing curtain ofthe focal plane shutter is released to start moving (step S438).Subsequently, the ports Pm2 and Pm3 are initialized (step S439), andcontrol returns to the camera main process. In the case where wirelesscontrol is performed, the successive sync flash mode is never designated(step S431, NO).

[0277] The cases where it is determined at step S402 that the sync modesetting does not designate the flat emission mode have been discussedabove. If it is determined at step S402 that the sync mode settingdesignates the flat emission mode, control proceeds from step S402 tostep S406 shown in FIG. 18. At step S406, the wireless signal intervalTW1M serving as the main-flash emission command wireless signal isdetermined from the following equation:

TW 1 M=2+(Tfp×64)/1000 (ms),

[0278] and is stored in the RAM 13 a.

[0279] Subsequently, it is determined whether the WLset flag is 1 (stepS407). If the WLset flag is 1 (if YES at step S407), the flash modesetting is set to designate the flat emission mode (step S408), and istransmitted as CF information from the camera body 10 to the externalflash device via the CF communication (step S409). Subsequently, themode-4 communication is performed (step S410). In the mode-4communication, a pulse signal having four successive pulses is output tothe external flash device. Upon receipt of the pulse signal having foursuccessive pulses, the external flash device firstly emits twosuccessive low flash emissions at the wireless signal interval TW1Mdetermined at step S406, and subsequently emits a uniform flash-emissionsimultaneously with the uniform flash-emission of the slave flashdevice. FIG. 6C shows the waveform of the uniform flash-emission at thetime of the main flash exposure when the flash mode setting designatesthe flat emission mode. The duration (“Tmain” shown in FIG. 6C) of theuniform flash-emission interval corresponds to the wireless signalinterval TW1M determined at step S406.

[0280] Subsequently, control waits for a time [(TW1M+2 ms−Tcop) ms](step S411) in order to complete the transmission of the main-flashemission command wireless signal in order to start the uniformflash-emission 2 ms before the leading curtain of the focal planeshutter starts moving. “Tcop” at step S411 represents the time lag ofthe leading curtain of the shutter between the moment the leadingcurtain is commanded to start moving and the moment the leading curtainactually starts moving.

[0281] Subsequently, the timer B is started in order to make the leadingcurtain start moving (step S412). Subsequently, it is determined whetherthe timer-B lapsed flag is 1 (step S424). If the timer-B lapsed flag isnot 1 (if NO at step S424), control repeats the checking operation atstep S424. If the timer-B lapsed flag is 1 (if YES at step S424),control proceeds to step S438 shown in FIG. 17 at which the trailingcurtain is released to start moving. Subsequently, the ports Pm2 and Pm3are initialized (step S439), and control returns to the camera mainprocess.

[0282] If the WLset flag is not 1 (if NO at step S407), control proceedsto step S413. At step S413 it is determined whether the WLint flag is 1.If the WLint flag is 1 (if YES at step S413), the timer C is set for atime (TW1M−Tmode 4), and the timer C is started (step S414). “Tmode 4”at step S414 represents the time necessary for the mode-4 communication.After the timer C is started, the built-in flash low flash emissionprocess is performed to activate the built-in flash to emit a low flashemission for 30 μs as a wireless signal which is transmitted the slaveflash device (step S415). Subsequently, it is determined whether atimer-C lapsed flag is 1 (step S416) If the timer-C lapsed flag is not 1(if NO at step S416) control repeats the checking operation at stepS416. If the timer-C lapsed flag is 1 (if YES at step S416), the mode-4communication is performed to command the external flash device to emita uniform flash-emission (step S417), and subsequently the built-inflash low flash emission process is performed again to activate thebuilt-in flash to emit a low flash emission for 30 μs as a wirelesssignal which is transmitted the slave flash device (step S418). Sincethe mode-4 communication at step S417 and the operation of transmittingthe main-flash emission command wireless signal to the slave flashdevice are completed at substantially the same time due to theoperations at steps S414 through S418, the external flash device and theslave flash device start emitting a uniform flash-emission at the sametime.

[0283] Subsequently, the timer C is set for a time [(2 ms −Tcop) ms],the timer-C lapsed flag is set to 0, and the timer C is started (stepS419). Subsequently, it is determined whether the timer-C lapsed flag is1 (step S420) If the timer-C lapsed flag is not 1 (if NO at step S420),control repeats the checking operation at step S420. The reason whycontrol waits at step S420 is to complete the transmission of themain-flash emission command wireless signal 2 ms before the leadingcurtain of the focal plane shutter starts moving. If the timer-C lapsedflag is 1 (if YES at step S420), the timer B set at step S401 is startedin order to make the leading curtain start moving (step S421).Subsequently, it is determined whether the timer-B lapsed flag is 1(step S424). If the timer-B lapsed flag is not 1 (if NO at step S424),control repeats the operation at step S424. If the timer-B lapsed flagis 1 (if YES at step S424), control proceeds to step S438 at which thetrailing curtain of the focal plane shutter is released to start moving.Subsequently, the ports Pm2 and Pm3 are initialized (step S439), andcontrol returns to the camera main process.

[0284] If the WLint flag is not 1 (if NO at step S413), namely, if awireless control is not performed, the mode-4 communication is performed(step S422), and control waits a time [(2 ms-Tcop) ms] (step S423-1).The reason why control waits this time at step S423-1 is to start theuniform flash-emission of the external flash device 2 ms before theleading curtain of the focal plane shutter starts moving. After thelapse of the time [(2 ms−Tcop) ms] at step S423-1, the timer B set atstep S401 is started to make the leading curtain start moving (stepS423-2). Subsequently, it is determined whether the timer-B lapsed flagis 1 (step S424). If the timer-B lapsed flag is not 1 (if NO at stepS424), control repeats the checking operation at step S424. If thetimer-B lapsed flag is 1 (if YES at step S424), control proceeds to stepS438 shown in FIG. 17 at which the trailing curtain is released to startmoving. Subsequently, the ports Pm2 and Pm3 are initialized (step S439),and control returns to the camera main process.

[0285] [Test-Flash Emission Process]

[0286] The test-flash emission process performed at step S168 will behereinafter discussed in detail with reference to the flow chart shownFIG. 19. In the test-flash emission process, the flash device 50 (theexternal flash device and/or the slave flash device) discharges only forthe purpose of checking the operating distance of the flash device 50.The test-flash emission process is performed when the test-flash settingswitch of the group of information setting switches 9 is switched ON.

[0287] In the test-flash emission process, each of the pre-flashintensity PreP and the pre-flash duration PreT is set to 1, and thewireless signal interval TW1M is set to 6.2 ms (step S450).Subsequently, the flash mode setting is set to designate the test flashmode (step S451) and is transmitted as CF information from the camerabody to the external flash device via the CF communication (step S452).After the CF communication is performed, it is determined whether theWLint flag is 1 (step S453).

[0288] If the WLint flag is not 1 (if NO at step S453), the mode-4communication is performed to command the external flash device to emita test flash emission (step S454), and subsequently control proceeds tostep S460-1.

[0289] On the other hand, if the WLint flag is 1 (if YES at step S453),the timer B is set for the value of the wireless signal interval TW1Mfrom which the value of the time necessary for the mode-4 communicationis subtracted, and the timer B is started (step S455). After the timer Bis started, the built-in flash low flash emission process is performedto drive the built-in flash to emit a low flash emission for 30 μs as awireless signal which is transmitted the slave flash device (step S456),and subsequently it is determined whether the timer-B lapsed flag is 1(step S457). If the timer-B lapsed flag is not 1 (if NO at step S457),control repeats the operation at step S457. If the timer-B lapsed flagis 1 (if YES at step S457), the mode-4 communication is performed again(step S458), and subsequently the built-in flash low flash emissionprocess is performed again (step S459). Subsequently, control proceedsto step S460-1. Since the mode-4 communication at step S459 and theoperation of transmitting the test-flash emission command wirelesssignal to the slave flash device are completed at substantially the sametime due to the operations at steps S455 through S459, the externalflash device and the slave flash device start emitting a test flashemission at the same time.

[0290] It is determined at step S460-1 whether the WLset flag is 1. Ifthe WLset flag is 1 (if YES at step S460-1) control waits a timecorresponding to the wireless signal interval TW1M stored in the RAM 13a (step S460-2). The waiting operation at step S460-2 is performed forthe purpose of waiting for the transmission of the test-flash emissioncommand wireless signal by the external flash device to be completed. Ifthe WLset flag is not 1 (if NO at step S460-1), control skips theoperation at step S460-2, and proceeds straight from step S460-1 to stepS461.

[0291] Subsequently, the pre-flash data determination process(“Pre-Flash Data Determination Process” shown in FIG. 14) is performed(step S461). Subsequently, two test light-magnifications Lev1 and Lev 2are calculated in accordance with the two flashlight-emittingmagnifications Mv1 and Mv2 which have been calculated in the pre-flashdata determination process (step S462). Subsequently, the calculatedtest light-magnifications Lev1 and Lev 2 are indicated on theinformation display panel 5 (step S463), and control returns to thecamera main process. In the present embodiment of the flash photographysystem, the test light-magnifications Lev1 and Lev2 are calculated usingthe following equations:

Lev 1=4−Mv 1,

[0292] and

Lev 2=4−Mv 2.

[0293] Fundamental operations of the flash device 50 will be hereinafterdiscussed with reference to the flow charts shown in FIGS. 20 through29.

[0294] [Flash Main Process]

[0295]FIG. 20 is a flow chart for a flash main process performed by theflash CPU 65 of the flash device 50. Immediately after the battery 51 isloaded in the flash device 50, control enters the flash main processafter the flash CPU 65 is initialized.

[0296] In the flash main process, firstly all interrupts are disabled,and each port of the flash CPU 65 is initialized (step S500).Subsequently, the flash CPU 65 has communication with the EEPROM 60 toread out initial data therefrom via the group of ports Pc (step S501).Subsequently, a reload timer set for 125 ms is set as a timer A, and thetimer A is started (step S502). Subsequently, an interrupt from thecamera body 10 is enabled, while an interrupt of a PWC timer (orcounter) for measuring a time interval between low flash emissions(light signals) that the light-receiving element 57 of the flash device50 receives is disabled (step S503). Subsequently, an F_CRequest flag isset to 1 while an F_WLs flag is set to 0 (step S504). The F_CRequestflag is set to 1 when it is necessary to charge the main capacitor 79 upto the maximum. The F_WLs flag is set to 1 when the wireless modesetting for the slave flash device has been completed.

[0297] Subsequently, it is determined whether the main switch 64 is OFFby checking the level of each of the input ports P0 and P1 (step S505).If the main switch 64 is OFF (if YES at step S505), both the input portsP0 and P1 are “1”. If the main switch 64 is OFF (if YES at step S505),the output port P2 is set to “1” to stop the operation voltage step upcircuit 66 (step S516). Subsequently, both a communication interruptfrom the camera body and an interrupt of the PWC timer are disabled(step S517), an ON-interrupt of each of the input ports P0 and P1 isenabled (step S518), and the flash CPU 65 enters a sleep mode (stepS519). In the sleep mode at step S519, since an ON-interrupt of each ofthe input ports P0 and P1 is enabled, an interrupt occurs and controlreturns to the operation at step S500 if the main switch 64 is switchedto the ON or WL (wireless) position.

[0298] If the main switch 64 is not OFF, namely, if the main switch 64is in the ON position or the WL position (if NO at step S505), acharging process of charging the main capacitor 79 is performed (stepS506). In the charging process, the output port P2 is set to “0” toactuate the voltage step up circuit 66 to charge the main capacitor 79via the diode 67. Immediately after the main capacitor 79 starts beingcharged, a voltage Hv′ which is identical to the terminal voltage acrossthe main capacitor 79 is input to the state-of-charge detecting circuit69. The voltage Hv′ input to the state-of-charge detecting circuit 69 isdivided via resistors provided in the state-of-charge detecting circuit69 to be output as an output voltage RLS from the state-of-chargedetecting circuit 69 to be input to the flash CPU 65 via the A/Dconversion port Pad thereof. In the present embodiment of the flashphotography system, the resistance ratio in the state-of-chargedetecting circuit 69 is determined so that the output voltage RLSbecomes 3.3V when the input voltage Hv′ is 330V and so that the outputvoltage RLS becomes 2.7V when the input voltage Hv′ is 270V.Furthermore, a Charge flag is set to 1 if the output voltage RLS becomesequal to or greater than 2.7V, and the charging operation stops if theoutput voltage RLS becomes equal to or greater than 3.3V.

[0299] After the charging process is performed, a switch settinginformation input process for inputting the switch settings set via thegroup of information setting switches 63 is performed (step S507) andsubsequently a communication information process is performed (stepS508). In the communication information process, each flash mode isreset in accordance with the CF information (see Table 3), which istransmitted from the camera body 10 to the external flash device (theflash device 50), while the set FC information (see Tables 1 and 2) isoutput to the camera body 10. The FC information includesphotometering-range checking information for confirming thephotometering distance range, and is transmitted to the camera body 10.

[0300] Subsequently, a wireless mode process (“Wireless Mode Process”shown in FIG. 21) is performed (step S509) In the wireless mode process,a wireless mode (a wireless slave mode, the old-system compatible mode,a wireless controller mode or a wireless control disabled mode) is setin accordance with the wireless mode setting input in the communicationinformation process at step S508. Subsequently, an indication process inwhich the flash information processed via the operations at steps 506through S509 are indicated on the Information display panel 72 isperformed (step S510). The information indicated on the Informationdisplay panel 72 at step S510 includes photometering mode information,sync mode information, wireless mode information, charge completioninformation, information on focal length that a flash emission cancover, maximum photometering distance information and minimumphotometering distance information.

[0301] After the indication process is performed at step S510, a zoomprocess in which the light emitting unit 55 (see FIG. 4B) is moved inaccordance with the lens focal length information input via the CFcommunication is performed (step S511-1) and subsequently an old-systemprocess is performed (step S511-2). In the old-system process, thecharge completion signal and an Fpulse signal which corresponds to thef-number set on the flash device 50 are transmitted to the camera bodyvia the terminal connector 56 if the camera body is a conventional typewhich cannot have communication with the flash CPU 65.

[0302] After the old-system process is performed, the flash CPU 65enters a low speed CPU mode (step S512) and subsequently it isdetermined whether the timer-A over flag is 1 (step S513). If thetimer-A lapsed flag is not 1 (if NO at step S513), control repeats theoperation at step S513. If the timer-A lapsed flag is 1 (if YES at stepS513), the flash CPU 65 enters a high speed CPU mode (step S514).Subsequently, the timer-A lapsed flag is set to 0 (step S515) andsubsequently control returns to the operation at step S505. Accordingly,the timer A, which is set for 125 ms, restarts every time it expires, sothat the operations at steps S505 through S515 are performed every 125ms.

[0303] [Wireless Mode Process]

[0304] The wireless mode process performed at step S509 will behereinafter discussed in detain with reference to the flow chart shownFIG. 21. In this process, firstly, it is determined whether the mainswitch 64 is in the WL position by checking the level of the input portP1 (step S550). The input port P1 is “0” if the main switch 64 is in theWL position.

[0305] If the main switch 64 is in the WL position (if YES at stepS550), it is determined whether the WLreq flag is 1 (step S550). TheWLreq flag is set to 1 when the wireless mode is either the wirelesscontroller mode or the wireless master mode. Namely, the flash device 50serves as external flash device if the WLreq flag is 1, or as slaveflash device if the WLreq flag is not 1.

[0306] If the WLreq flag is not 1 (if NO at step S551), it is determinedwhether a photometering mode request BLo which has been previouslystored last at step S557 is not equal to the currently-set photometeringmode request (step S552-1) If it is the first time for control to enterthe wireless mode process, the photometering mode request BLo iscompared with a default value stored in the RAM 13 a. If thephotometering mode request BLo is not equal to the currently-setphotometering mode request (if YES step at S552-1), the F_WLs flag isset to 0 to renew the photometering mode (step S552-2). If thephotometering mode request BLo is equal to the currently-setphotometering mode request (if NO at step S552-1) control proceeds fromstep S552-1 to step S553. It is determined at step S553 whether theF_WLs flag is 1. The F_WLs flag is set to 1 when the wireless modesetting for the slave flash device has been completed. If F_WLs flag is1 (if YES at step S553), control returns to the flash main process shownin FIG. 20.

[0307] If F_WLs flag is not 1 (if NO at step S553), all communicationinterrupts are disabled (step S554). Subsequently, all the communicationports of the terminal connector 56, the camera-flash communicationinterface 59 and the group of ports Pd of the flash CPU 65 are allchanged to input ports, while the discharge of the external flash deviceupon a change of the terminal X from “1” to “0” is disabled (step S555)(see FIG. 34). When the flash device 50 serves as slave flash device, itis generally the case the flash device 50 is fixed via a clip with a hotshoe (not shown) or via a flash st and with a hot shoe (not shown) thatis available on the market. However, since various hot shoe accessoriesare available on the market, it is sometimes the case that a shortcircuit occurs when the flash device 50 outputs a signal or that theterminal X is turned ON accidentally when the base of the flash device50 is fixed to a hot shoe. The operation at step S555 is performed toprevent the flash device 50 from being damaged due to such a shortcircuit and from discharging accidentally due to the terminal X beingturned ON accidentally.

[0308] Subsequently, the lens focal length information is set to aninitial value of 24 mm while each of the pre-flash intensity PreP andthe pre-flash duration PreT is set to 1 (step S556). The currentphotometering mode request is stored in the RAM 13 a as theaforementioned photometering mode request BLo (step S557). Subsequently,it is determined whether the photometering mode request requests the TTLphotometering mode (step S558).

[0309] If the photometering mode request requests the TTL photometeringmode (step S558), the discharging operation of the slave flash device iscontrolled in a first flash emission control mode. In the first flashemission control mode, the slave flash device receives the pre-flashemission command wireless signal, the light-magnification commandwireless signal and the main-flash emission command wireless signalsuccessively in that order, which are transmitted from the camera body10, and controls the discharging operation of the slave flash device inaccordance with the received signal.

[0310] However, if the photometering mode request requests the autoflash photometering mode or the manual photometering mode, the flash CPU65 can control the amount of light of the flash emission independentlywithout receiving any command wireless signals, so that the dischargingoperation of the slave flash device is controlled in a second flashemission control mode. In the second flash emission control mode, theslave flash device starts discharging immediately after the amount ofthe light received by the light-receiving element 57 reaches apredetermined value.

[0311] If the photometering mode request requests the TTL photometeringmode (if YES at step S558), the measuring mode of the PWC timer is setto a mode of measuring an interval between trailing edges of low flashemissions (wireless signals) that the light-receiving element 57 of theflash device 50 receives (step S559). Subsequently, an interrupt of thePWC timer is enabled (step S560), and the PWC timer is started tothereby enter a state where light signal (wireless signal) can bereceived. Subsequently, the PWC timer is started (step S561), and avariable WLmode is set to 1, the F_WLs flag is set to 1, and a variableWLstep is set to 0 (step S562). Subsequently control returns to theflash main process shown in FIG. 20. The value of the variable WLmoderepresents the currently-set wireless mode. The variable WLmode of “1”represents the wireless slave mode. The value of the variable WLsteprepresents the state in receiving the wireless signal. The variableWLstep of “0” represents the standby state of receiving the pre-flashemission command wireless signal. The variable WLstep of “1” representsthe standby state of receiving the light-magnification command wirelesssignal. The variable WLstep of “2” represents the standby state ofreceiving the main-flash emission command wireless signal.

[0312] After the operations at steps S559 through S562 are performed, aninterrupt of the PWC timer occurs immediately after the first trailingedge of the waveform of the received wireless signal is given to thegroup of ports Pe of the flash CPU 65, i.e., immediately after theamount of the light received by the light-receiving element 57 reaches apredetermined value. If an interrupt of the PWC timer occurs, a PWCinterrupt process (“PWC Interrupt Process” shown in FIGS. 27 and 28)starts. In the PWC interrupt process, it is determined that the receivedwireless signal represents which command (the pre-flash command, thelight-magnification command, the main flash command or the test flashcommand) in accordance with data represented by the interval between twotrailing edges of the received wireless signal, and predeterminedoperations are performed in accordance with the command represented bythe received wireless signal.

[0313] If the photometering mode request does not request the TTLphotometering mode (if NO at step S558), it is determined whether theold-system compatible mode has been set (step S563). In the presentembodiment of the flash photography system, the new-system compatiblemode, in which the slave flash device starts emitting the main flash ata time of exposure upon receiving more than one light signal (wirelesssignal) successively, and the old-system compatible mode, in which theslave flash device starts emitting the main flash at a time of exposureupon an amount of a single flash emission emitted by the built-in flashof the camera body 10 or the external flash device reaching apredetermined value, can be switched if the auto flash photometeringmode or the manual photometering mode is selected via the photometeringmode request setting switch 63 a. The new-system compatible mode and theold-system compatible mode can be manually switched via the systemselector switch 63 d. The old-system compatible mode is selected by theuser when a conventional camera which cannot transmit any wirelesssignal or cannot make the external flash device transmit any wirelesssignal is used, or when a conventional type flash device which cannottransmit any wireless signal is used as a master flash device or acontroller flash. The new-system compatible mode and the old-systemcompatible mode can be stored in the EEPROM 60 as selection data whichcan be selected via, e.g., a multi-function select button.

[0314] If the old-system compatible mode has been set (if YES at stepS563), the measuring mode of the PWC timer is set to a counter mode sothat the slave flash device can start discharging in synchronizationwith a single low flash emission emitted by the built-in flash of thecamera body 10 or the external flash device (step S564). Subsequently,an interrupt of a PWC counter is enabled (step S565). Subsequently, aregister PWCR which represents a PWC counter value is loaded with FFFF,and the PWC timer is started (step S566). Subsequently, the variableWLmode is set to 2, and the F_WLs flag is set to 1 (step S567).Subsequently control returns to the flash main process shown in FIG. 20.The variable WLmode of “2” represents the old-system compatible mode. Inthe old-system compatible mode, the register PWCR is increased by one tothereby change the value of the register PWCR from FFFF to 0000immediately after the light-receiving element 57 receives a single flashemission emitted by the built-in flash of the camera body 10 or theexternal flash device, i.e., immediately after the first trailing edgeof the waveform of the received wireless signal shown in FIG. 6E or 6Fis given to the group of ports Pe of the flash CPU 65. This change ofthe value of the register PWCR causes an interrupt of the PWC timer tooccur, so that the PWC interrupt process shown in FIGS. 27 and 28starts, thus causing the slave flash device to discharge.

[0315] If the new-system compatible mode has been set (if NO at stepS563), control proceeds to step S559. In this case, the slave flashdevice emits the main flash at a time of exposure by receiving thepre-flash emission command wireless signal, the light-magnificationcommand wireless signal and the main-flash emission command wirelesssignal successively in that order.

[0316] If the WLreq flag is 1 (if YES at step S551), it is determinedwhether the WLset flag is 1 (step S568). If the WLset flag is not 1 (ifNO at step S568), control proceeds to step S570. If the WLset flag is 1(if YES at step S568), the variable WLmode is set to 3 (step S569), andsubsequently control proceeds to step S571. The variable WLmode “3”represents the mode in which the slave flash device is controlled bywireless.

[0317] If the main switch 64 is not in the WL position (if NO at stepS550), control proceeds to step S570. At step S570 the variable WLmodeis set to 4 and subsequently control proceeds to step S571. The variableWLmode “4” represents the mode in which wireless control is notperformed. It is determined at step S571 whether the F_WLs flag is 1. Ifthe F_WLs flag is not 1, control returns to the flash main process. Ifthe F_WLs flag is 1 (if YES at step S571), control proceeds to step S572to cancel the settings of the slave flash device. Namely, all thecommunication ports of the terminal connector 56 are initialized whileall communication interrupts are enabled (step S572), the discharge ofthe flash device 50 upon a change of the terminal X from “1” to “0” isenabled (step S573), an interrupt of either the PWC timer or the PWCcounter is disabled (step S574), and the F_WLs flag is set to 0 (stepS575). Subsequently, control returns to the flash main process shown inFIG. 20.

[0318] In the above described wireless mode process, in the case wherethe flash device 50 serves as slave flash device, control proceeds fromstep S551 to step S552-1 to perform the operations at steps S552-1through S567 since the WLreq flag is set to 0, i.e., since the mainswitch 64 is in the WL position and at the same time the wireless modesetting switch 63 c is in the wireless slave mode.

[0319] In the case where the flash device 50 serves as external flashdevice and controls the slave flash device by wireless, control proceedsfrom step S551 to step S568 to perform the operations at steps S568,S569 and S570 through S575 since the WLreq flag is set to 1, i.e., sincethe main switch 64 is in the WL position and at the same time thewireless mode setting switch 63 c is in either the wireless controllermode or the wireless master mode.

[0320] In the case where the flash device 50 serves as external flashdevice but does not control the slave flash device by wireless control,control proceeds from step S568 to step S570 to perform the operationsat steps S570 through S575 since the main switch 64 is not in the WLposition.

[0321] [Communication Interrupt Process]

[0322] The communication interrupt process performed on condition thatthe main switch 64 is in either the ON position or the WL position willbe hereinafter discussed in reference to the flow chart shown in FIG. 22and the timing charts shown in FIGS. 5 and 6A through 6F. Thecommunication interrupt process is performed upon the variation of theterminal C of the terminal connector 56 from “0” to “1” or from “1” to“0” since an interrupt from the camera body 10 is enabled at step S503.

[0323] In the communication interrupt process, firstly no communicationinterrupt from the camera body 10 is enabled to disable the subsequentcommunication interrupt from the camera body 10 (step S600).Subsequently, the current CPU speed of the flash CPU 65 is stored in aRAM 65 a, while the flash CPU 65 enters the high speed CPU mode (stepS601). Subsequently, the waveform of the control signal input from thecamera body 10 via the terminal C of the terminal connector 56 ischecked (step S602). The flash CPU 65 reads the contents of thecommunications by reading the waveform of the control signal input fromthe camera body 10, and performs the operations at and after step S603.

[0324] At step S603 it is determined whether the waveform of the inputcontrol signal carries only a single pulse. If YES at step S603, the CFcommunication in which CF information shown in Table 3 is input from thecamera body 10 via the terminal Q of the terminal connector 56 insynchronization with the clock signal input to the terminal R of theterminal connector 56 is performed (step S604) (see (b) in FIG. 5).After the CF communication is performed at step S604, a CF informationresetting process in which predetermined modes of the flash device 50are reset in accordance with the input CF communication data isperformed (step S605), and the CPU speed of the flash CPU 65 is changedto the CPU speed stored in the RAM 65 a at step S601 (step S617).Subsequently, a communication interrupt from the camera body 10 isenabled (step S618) and control returns to the step where thecommunication interrupt occurs.

[0325] If NO at step S603, it is determined whether the waveform of theinput control signal carries two successive pulses (step S606). If YESat step S606, the FC communication is performed, wherein FC informationshown in Table 1 is output from the flash device 50 (external flashdevice) to the camera body 10 via the terminal Q of the terminalconnector 56 in synchronization with the clock signal input to theterminal R of the terminal connector 56 (step S607) (see (c) in FIG. 5).

[0326] If NO at step S606, it is determined whether the waveform of theinput control signal carries three successive pulses (step S608). If YESat step S608, a normal flash emission process (“Normal Flash EmissionProcess” shown in FIG. 26) is performed (step S609).

[0327] If NO at step S608, it is determined whether the waveform of theinput control signal carries four successive pulses (step S610). If YESat step S610, a special flash emission process (“Special Flash EmissionProcess” shown in FIG. 23) is performed (step S611). In the specialflash emission process, the flash device 50 performs predeterminedoperations in accordance with the currently-set flash mode setting.

[0328] If NO at step S610, it is determined whether the waveform of theinput control signal carries only a leading edge (step S612). If YES atstep S612 (see (a) in FIG. 5), an F_COn flag is set to 1 (step S613),and the F_CRequest is set to 1 (step S614) Subsequently, controlproceeds to step S617. The F_COn flag is set to 1 and 0 when the camerais in a state of working and a non-working state, respectively.

[0329] If NO at step S612, it is determined whether the waveform of theinput control signal carries only a trailing edge (step S615). If YES atstep S615 (see (d) in FIG. 5), an F_COn flag is set to 0 (step S616).Subsequently, control proceeds to step S617. If the F_COn flag remains 0for over a predetermined period of time (e.g., five minutes), the flashCPU 65 enters the sleep mode to reduce the power consumption thereof.

[0330] If NO at step S615 (i.e., if the waveform of the input controlsignal does not bear any of one through four pulses or even any leadingor trailing edge), control proceeds to step S617 at which the CPU speedof the flash CPU 65 is changed to the CPU speed stored in the RAM 65 aat step S601. Subsequently, a communication interrupt from the camerabody 10 is enabled (step S618) and control returns to the step where thecommunication interrupt occurs.

[0331] [Special Flash Emission Process]

[0332] The special flash emission process performed at step S611 will behereinafter discussed in detail with reference to the flow chart shownFIGS. 23 and 24. The special flash emission process is performed whenthe flash device 50 inputs the waveform of the control signal carryingfour successive pulses via the terminal C of the terminal connector 56.In the special flash emission process, firstly it is determined whetherthe variable WLmode is 3 (step S650). The variable WLmode “3” representsthe mode in which the slave flash device is controlled by wirelesscontrol.

[0333] If the variable WLmode is 3 (if YES at step S650), a variable numis set to 1 (step S651), and subsequently the external flash deviceemits two successive low flash emissions serving as a wireless signal (apre-flash emission command wireless signal) via operations at steps S652through S667.

[0334] It is determined whether the flash mode setting designates thepre-flash emission mode (step S652). If the flash mode settingdesignates the pre-flash emission mode (if YES at step S652), it isdetermined whether the sync mode setting designates the flat emissionmode (step S653-1). If the sync mode setting designates the flatemission mode (if YES at step S653-1), the wireless signal interval TW1Mis set to 5.2 ms (step S653-2) and subsequently control proceeds to stepS661 shown in FIG. 24. If the sync mode setting does not designate theflat emission mode (if NO at step S653-1), it is determined whether thepre-flash emission mode PreM is 1 (step S653-3). If the pre-flashemission mode PreM is 1 (if YES at step S653-3), the wireless signalinterval TW1M is set to 4.2 ms (step S653-4) and subsequently controlproceeds to step S661. If the pre-flash emission mode PreM is not 1 (ifNO at step S653-3), the wireless signal interval TW1M is set to 3.2 ms(step S653-5) and subsequently control proceeds to step S661.

[0335] If the flash mode setting does not designate the pre-flashemission mode (if NO at step S652), it is determined whether the flashmode setting designates the test flash mode (step S654). If the flashmode setting designates the test flash mode (if YES at step S654), thewireless signal interval TW1M is set to 6.2 ms (step S655) andsubsequently control proceeds to step S661.

[0336] If the flash mode setting does not designate the test flash mode(if NO at step S654), it is determined whether the flash mode settingdesignates the flat emission mode (step S656). If the flash mode settingdesignates the flat emission mode (if YES at step S656), the wirelesssignal interval TW1M is set at the value calculated from theaforementioned equation “TW1M=2 ms+(Tfp×64)/1000 (ms)” (at step S657),and subsequently control proceeds to step S661. “Tfp” in this equationdesignates the uniform flash-emission duration Tfp (ms). The uniformflash-emission duration Tfp of the slave flash device is determined bythe wireless signal interval TW1M determined at step S406 if the flashmode setting designates the flat emission mode.

[0337] If the flash mode setting does not designate the flat emissionmode (if NO at step S656), it is determined whether the flash modesetting designates the light-magnification flash mode (step S658). Ifthe flash mode setting designates the light-magnification flash mode (ifYES at step S658), the wireless signal interval TW1M is set to the valuecalculated from the aforementioned equation “TW1M=2 ms+(Mv1+5)×128/1000(ms)”, and subsequently the wireless signal interval TW2M is set to thevalue calculated from the aforementioned equation “TW2M=2ms+(Mv2+5)×128/1000 (ms)” (step S659). Subsequently, it is determinedwhether the pre-flash emission mode PreM is 1 (step S660-1). If thepre-flash emission mode PreM is 1 (if YES at step S660-1), the variablenum is set to 2, and subsequently control proceeds to step S661 shown inFIG. 24. If the pre-flash emission mode PreM is not 1 (if NO at stepS660-1), control proceeds straight from step S660-1 to step S661 shownin FIG. 24.

[0338] If the flash mode setting does not designate thelight-magnification flash mode (if NO at step S658) control proceeds tostep S668.

[0339] Table 6 below shows the one-to-one correspondence between theflash mode setting and the wireless signal interval TW1M. TABLE 6Interval Flash Mode Setting Condition [ms] Waveform Pre-Flash EmissionPreM = 0 3.2 Tw1 Mode PreM = 1 4.2 Tw1 Sync Mode Setting = 5.2 Tw1 FlatEmission Test Flash 6.2 Tw1 Emission Mode Light-Magnification WM = 2˜3Tw1, Tw2 on Flash Emission Mode Flat Emission Sync Mode Setting = WT =2˜3 Tw1 Flat Emission (Main Flash Flash Mode Other (1) *1 Emmission *1Than Flat Emission Mode

[0340] At step S661, the timer B is set for the value of the wirelesssignal interval TW1M, and the timer B is started (step S661). After thetimer B is started, a low flash emission process is performed (stepS662). In the low flash emission process, the xenon flashtube 82 of theflash device 50 is activated to discharge to emit a low flash emissionfor 30 μs as a wireless signal which is transmitted the slave flashdevice. More specifically, in the flash emission process, the signal30Von, which is output from the output port P4 of the flash CPU 65 to beinput to the 30-volt generating circuit 77, is set to “1”, and at thesame time the signal IGBTctl, which is output from the output port P5 tobe input to the level shift circuit 78, is set to “1” to switch the IGBT83 ON. In the ON state of the IGBT 83, a signal TRIGon, which is outputfrom the output port P3 of the flash CPU 65 to be input to the triggercircuit 80, is set to “1” to thereby cause the xenon flashtube to startdischarging. Thereafter, the signal IGBTctl is changed from “1” to “0”to switch the IGBT 83 OFF to thereby cause the xenon flashtube to stopdischarging upon the lapse of 30 μs since the signal TRIGon was set to“1”. In the operation at step S662, the xenon flashtube 82 of the flashdevice 50 is activated to discharge to emit the first low flashemission, which is represented by the first pulse (1) shown in FIG. 6Eor 6F.

[0341] After the low flash emission process is performed at step S662,it is determined whether the timer-B lapsed flag is 1 (step S663). Ifthe timer-B lapsed flag is not 1 (if NO at step S663), control repeatsthe checking operation at step S663. If the timer-B lapsed flag is 1 (ifYES at step S663), the low flash emission process is performed again(step S664). In the operation at step S664, the xenon flashtube 82 ofthe flash device 50 is activated to discharge to emit the second lowflash emission, which is represented by the second pulse (2) shown inFIG. 6E or 6F.

[0342] Subsequently, the variable num is decremented by one (step S665)and it is determined whether the variable num is 0 (step S666). If thevariable num is not 0 (if NO at step S666), the timer B is set to thevalue of the wireless signal interval TW2M, and the timer B is started(step S667), and subsequently control returns to step S663 to emit thethird low flash emission, which is represented by the third pulse (3)shown in FIG. 6F. If the variable num is 0 (if YES at step S666),control proceeds to step S668 since the wireless signal transmittingoperation in the special flash emission process has been completed.

[0343] At step S668, it is determined whether the wireless master modehas been set via the wireless mode setting switch 63 c and whether thecurrently-set flash mode setting designates one of the pre-flashemission mode, the flat emission mode, or the test flash mode. If thewireless master mode has been set and the currently-set flash modesetting designates the pre-flash emission mode, the flat emission modeor the test flash mode (if YES at step S668), a uniform flash-emissionprocess (Uniform flash-emission Process” shown in FIG. 25) is performedin accordance with the flash mode setting (step S670). The operation atstep S668 considers the case where the wireless master mode has been setand where more than one flash is used. After the uniform flash-emissionprocess is performed, the F_CRequest flag is set to 1 (step S671), andcontrol returns to the communication interrupt process shown in FIG. 22.

[0344] If the variable WLmode is not 3 at step S650, the uniformflash-emission process is performed in accordance with the flash modesetting (step S670), subsequently the F_CRequest flag is set to 1 (stepS671) and subsequently control returns to the communication interruptprocess shown in FIG. 22.

[0345] [Uniform flash-emission Process]

[0346] The uniform flash-emission process performed at step S670 will behereinafter discussed in detail with reference to the timing chart shownin FIG. 7 and the flow chart shown in FIG. 25.

[0347] In the uniform flash-emission process, firstly, a uniformflash-emission level (a pre-flash emission level) Vfp is calculated atstep S700 using the following equation:

Vfp=Va×T_fire(zoom)

[0348] wherein

[0349] “Va” represents the reference flash emission level; and “zoom”represents the zoom position (mm).

[0350] T_fire(zoom) is calculated using the following equation:

T_fire(zoom)≈( Gnos/Gno(zoom))²;

[0351] wherein Gnos represents the reference guide number.

[0352] The reference guide number Gnos is a constant which can be freelyset at any number. In the present embodiment of the flash photographysystem, the reference guide number Gnos is set at 36. Table 7 belowshows the relationship among the zoom position (focal length), the guidenumber Gno and the T_fire(zoom). The guide number Gno of A-type flash isgreater than that of B-type flash. TABLE 7 Flash Zoom Position Type (mm)24 28 35 50 70 8.5 A Gno 21 22 25 30 33 36 T_fire (zoom) 2.9 2.7 2.1 1.41.2 1 B Gno 35 36 39 44 47 50 T_tire (zoom) 1.06 1 0.85 0.67 0.58 0.52

[0353] In Table 7, the reference guide number Gnos “36” is the referenceguide number Gnos at the time a type-A flash device discharges at themaximum with the zoom position set at 85 mm, or at the time a type-Bflash device discharges at the maximum with the zoom position set at 28mm. The maximum guide number Gno varies in accordance with a variationof the zoom position, and is the value at the time each type flashdischarges at the maximum at each zoom position. The reference flashemission level Va is a constant for correcting the dispersion of theamount of flash light emission emitted by each flash, and is stored inthe EEPROM 60.

[0354] The zoom positions shown in Table 7 are determined by the flashCPU 65 so that an illumination angle suitable for the focal length ofthe photographing lens can be obtained. In the present embodiment of theflash photography system, the space between the Fresnel lens 55 a andthe light emitting unit 55 (see FIG. 4B) is represented by the zoomposition (mm) which is the converted value of the focal length f. Forinstance, the zoom position is set at 24 mm when the focal length f ofthe photographic lens is 24 mm. In this case, the light emitting unit 55is moved to a position where the space between the Fresnel lens 55 a andthe light emitting unit 55 corresponds to 24 mm (the focal length) ofthe photographing lens. If the flash device 50 is not connected to thecamera body 10, the zoom position can be set freely by the user.

[0355] It can be understood from Table 7 that the guide number Gnoincreases while the T_fire(zoom) decreases as the zoom position movesaway, i.e., as the focal length increases. According to the operation atstep S700, since the uniform flash-emission level Vfp is inverselyproportional to the value of the T_fire(zoom), the uniformflash-emission level Vfp decreases as the zoom position moves away.Consequently, the illuminance with respect to the object at a specifieddistance becomes constant regardless of a variation of the zoomposition, i.e., the effective guide number becomes constant if thedistances between flash devices in use to the object are all the same.

[0356] In the present embodiment of the flash photography system, sincethe reference guide number Gnos is constant regardless of flash type,the T_fire(zoom) on the B-type flash, whose guide number is greater thanthat of the A-type flash, is smaller than the T_fire(zoom) on the A-typeflash. Consequently, in the B-type flash, whose guide number isdifferent from that of the A-type flash, the illuminance with respect tothe object at a specified distance is constant regardless of a variationof the zoom position, i.e., the effective guide number is constant ifthe distances between flash devices in use to the object are all thesame.

[0357] After the uniform flash-emission level Vfp has been set at stepS700, it is determined whether the flash mode setting designates theflat emission mode (step S701). If the flash mode setting designates theflat emission mode (if YES at step S701), the operations at steps S702through S707 are performed to make preparations for the main flashexposure. If the flash mode setting does not designate the flat emissionmode (if NO at step S701), the operations at steps S708-1 through S713are performed to make preparations for the pre-flash emission or thetest flash emission.

[0358] If the flash mode setting designates the flat emission mode (ifYES at step S701), the flashlight-emitting magnification Mv is set tothe flashlight-emitting magnification Mv1 which has been input via CFcommunication (step S702). The flashlight-emitting magnification Mv1 isinput by CF communication if the flash device 50 serves as an externalflash device, and is set by the light-magnification command wirelesssignal if the flash device 50 serves as a slave flash device.Subsequently, it is determined whether the pre-flash emission mode PreMis 1 (step S703). The second pre-flash emission mode, in which all theflash devices except the built-in flash are driven to emit a pre-flashin a predetermined order, has been set when the pre-flash emission modePreM is 1. If the pre-flash emission mode PreM is 1 (if YES at stepS703), it is determined whether the sync mode request requests thesuccessive sync flash mode (step S704). If the sync mode requestrequests the successive sync flash mode (if YES at step S704), theflashlight-emitting magnification Mv is set to the flashlight-emittingmagnification Mv2 which has been input from via CF communication (stepS705), and control proceeds to step S706. The flashlight-emittingmagnification Mv2, similar to the flashlight-emitting magnification Mv1,is input by CF communication if the flash device 50 serves as anexternal flash device, and is set by the light-magnification commandwireless signal if the flash device 50 serves as a slave flash device.If the pre-flash emission mode PreM is not 1 (if NO at step S703), or ifthe sync mode request does not request the successive sync flash mode(if NO at step S704) even if the pre-flash emission mode PreM is 1,control skips the operation at step S705, so that control proceedsstraight from step S703 to S706 or from step S704 to S706. At step S706,the output level of the voltage FPlvl, which is to be output. from theD/A conversion port Pda, is calculated using the following equation:

FPlvl=Vfp×2^(Mv);

[0359] and subsequently the voltage FPlvl is output from the D/Aconversion port Pda to be supplied to the non-inverting input terminalof the comparator 75. Subsequently, the timer B is set for the sum ofthe uniform flash-emission duration Tfp and 3 ms, and subsequently thetimer B is started (step S707). The time “3 ms” is added to the uniformflash-emission duration Tfp (mm) just in case the uniform flash-emissionduration Tfp is insufficient.

[0360] On the other hand, if the flash mode setting does not designatethe flat emission mode (if NO at step S701), it is determined whetherthe flash mode setting designates the test flash mode (step S708-1). Ifthe flash mode setting designates the test flash mode (if YES at stepS708-1), the output level of the voltage FPlvl is set to a voltage Vb,and subsequently the voltage FPlvl is output from the D/A conversionport Pda (step S708-2). The voltage Vb is determined so that the flashdevice 50 discharges at the inverse of specified times of the maximumlight amount of the flash emission (Mv=0EV) which can be emitted at eachzoom position of the flash device 50. In the present embodiment of theflash photography system, the voltage Vb is determined so that the flashdevice 50 discharges at an 1/16 (Mv=−4EV) at each zoom position of theflash device 50. The voltage Vb is stored in the EEPROM 60. If the flashmode setting does not designate the test flash mode (if NO at stepS708-1) the output level of the voltage FPlvl is calculated at stepS708-3 using the following equation:

FPlvl=Vfp×PreP;

[0361] and subsequently the voltage FPlvl is output from the D/Aconversion port Pda.

[0362] The pre-flash intensity PreP is determined via the abovedescribed operations at steps S202-1, S202-2 and S202-3 shown in FIG.12.

[0363] Subsequently, it is determined whether the pre-flash emissionmode PreM is 1 (step S709). If the pre-flash emission mode PreM is 1 (ifYES at step S709), it is determined whether the sync mode requestrequests the successive sync flash mode (step S710).

[0364] If the sync mode request requests the successive sync flash mode(if YES at step S710), the timer B is set to 2.5 ms and started (stepS711). Subsequently, it is determined whether the timer-B lapsed flag is1 (step S712). If the timer-B lapsed flag is not 1 (if NO at step S712),control repeats the checking operation at step S712. If the timer-Blapsed flag is 1 (if YES at step S712), the timer B is set to thepre-flash duration PreT (step S713) and subsequently control proceeds tostep S714.

[0365] If the pre-flash emission mode PreM is not 1 (if NO at stepS709), or if the sync mode request does not request the successive syncflash mode (if NO at step S710), control skips the operations at stepsS711 and S712, and therefore proceeds straight from step S709 to S713 orfrom step S710 to S713. In this case, the timer B is set for thepre-flash duration PreT at step S713 to emit the first pre-flashemission, which is represented by the first pulse (1) shown in FIG. 6D.Subsequently, control proceeds to step S714.

[0366] The time T0 shown in FIG. 7 shows an initial state of the uniformflash-emission process. In this initial state, the output ports P4 (thesignal 30Von), P5 (the signal IGBTctl) and P7 of the flash CPU 65 areall set to “0” via the operation at step S500. The port P6 is set toserve as an input port, while the voltage FPlvl is output from the D/Aconversion port Pda to be input to the non-inverting input terminal ofthe comparator 75. In this state, no voltage is applied to the triggerelectrode XeT of the xenon flashtube 82 since the output of the port P3,i.e., the signal TRIGon is “0”, so that the xenon flashtube 82 does notdischarge. Consequently, the voltage PDfl that is input to the invertinginput terminal of the comparator 75 is “0” since no photocurrent isoutput from the light-receiving element 85, so that the output of thecomparator 75 is “0”.

[0367] At step S714 the output port P4, i.e., the signal 30Von ischanged from “0” to “1” (at a time T1 shown in FIG. 7). Upon this changeof the signal 30Von, a voltage of 30 volts is output from the 30-voltgenerating circuit 77 to be applied to the level shift circuit 78.

[0368] Subsequently, the output port P5, i.e., the signal IGBTctl ischanged from “0” to “1” at step S715 (at a time T2 shown in FIG. 7).This causes the level shift circuit 76 to apply the voltage of 30V,which is given to the level shift circuit 76 from the 30-volt generatingcircuit 77, to the gate IGBTg of the IGBT 83 in order to switch the IGBT83 ON.

[0369] Subsequently, the output port P3, i.e., the signal TRIGon ischanged from “0” to “1” at step S716 (at a time T3 shown in FIG. 7).Upon this change of the signal TRIGon, the trigger circuit 80 applies anoscillating high voltage to the trigger electrode XeT of the xenonflashtube 82 to render xenon gas filled therein in an excitation stateto thereby cause the xenon flashtube 82 to discharge. Namely, theelectric charges accumulated in the main capacitor 79 are discharged viathe coil 81, the xenon flashtube 82 and the IGBT 83.

[0370] Subsequently, the timer B which has been set at step S707 or S713is started (step S717), the port P5, i.e., the signal IGBTctl is set toserve as an input port (step S718), and the output port P3, i.e., thesignal TRIGon is set to “0” (step S719). The state of the port P5 afterit has been set as input port at step S718 is equivalent to the statewhere the port P5 is electrically disconnected from each of the resistor76 and the comparator 78. In this state, the output of the comparator 75is input to the level shift circuit 78 as the signal IGBTctl. The reasonwhy the port P5 is set to serve as an input port at step S718 is thatthe comparator 75 and other elements may malfunction due to theoscillating high voltage applied to the trigger electrode XeT of thexenon flashtube 82. However, the xenon flashtube 23 discharges stablyeven if such a malfunction occurs by changing the port P5 from an outputport to an input port.

[0371] Upon a commencement of the discharge of the xenon flashtube 82due to the operation at step S716, the voltage PDfl that corresponds tothe amount of light emission of the xenon flashtube 82 is input to theinverting input terminal of the comparator 75. Subsequently, immediatelyafter the voltage PDfl reaches the voltage FPlvl (at a time T4 shown inFIG. 7), the output of the comparator 75, i.e., the signal IGBTctl,changes from “1” to “0” to thereby switch the IGBT 83 OFF via the levelshift circuit 78. In this state, the electric charges accumulated in themain capacitor 79 are stopped discharging via the IGBT 83, while theelectric charges accumulated in the coil 81 are discharged via the xenonflashtube 82 and the diode 84. This reduces the amount of light emissionof the xenon flashtube 82, and at the same time the voltage PDfl drops.Subsequently, immediately after the voltage PDfl becomes smaller thanthe predetermined voltage FPlvl (at a time T5 shown in FIG. 7), theoutput, i.e., the signal IGBTctl of the comparator 75 changes from “0”to “1” to thereby switch the IGBT 83 ON. This causes the xenon flashtube82 to resume discharging via the IGBT 83 to thereby increase the amountof light emission of the xenon flashtube 82. It is unnecessary to applythe oscillating high voltage to the trigger electrode XeT of the xenonflashtube 82 at the time T5 since the excitation state of the xenonflashtube 82 has continued at the time T5.

[0372] It is determined at step S720 whether the timer-B lapsed flagis 1. If the timer-B lapsed flag is not 1 (if NO at step S720), controlrepeats the checking operation at step S720. If the timer-B lapsed flagis 1 (if YES at step S720), control proceeds to step S721. The abovedescribed ON/OFF operation of the IGBT 83 is rapidly repeated until itis determined at step S720 that the timer-B lapsed flag is 1, andaccordingly the amount of light emission of the xenon flashtube 82 ismaintained substantially constant until the timer B (Tfp+3 ms) expires(see FIG. 6C).

[0373] If the timer-B lapsed flag is 1 (if YES at step S720), it isdetermined whether the output port P5, i.e., the signal IGBTctl, haschanged from “1” to “0” (step S721). If the output port P5 has not yetchanged from “1” to “0” (if NO at step S721), control repeats thechecking operation at step S721. Namely, control waits until the inputport P5, i.e., the signal IGBTctl, changes from “1” to “0” at step S721.This prevents the IGBT 84 from being damaged. If the signal IGBTctl ofthe output port P5 has changed from “1” to “0” (if YES at step S721),the port P5 is changed to an output port to output a signal of “0” tothereby switch the IGBT OFF (step S722). Subsequently, the F_CRequestflag is set to 1 (step S723) and control returns.

[0374] [Normal Flash Emission Process]

[0375] The normal flash emission process performed at step S609 will behereinafter discussed in detail with reference to the timing chartsshown in FIGS. 6A, 6B and the flow chart shown in FIG. 26. The normalflash emission process is performed when the control signal with threesuccessive pulses, which represents the normal-flash-emission commandsignal, is input to the flash CPU 65 via the terminal C thereof oncondition that the flash device 50 is coupled to the camera body 10 asexternal flash device (see FIGS. 6A and 6B).

[0376] In the normal flash emission process, firstly it is determinedwhether the terminal X is “0” (step S750). If the terminal X is not “0”(if NO at step S750), control repeats the checking operation at stepS750 until the terminal X becomes “0”. If the terminal X is “0” (if YESat step S750), it is determined whether the Charge flag is 1 (stepS751). If the Charge flag is not 1 (if NO at step S751), i.e., if theflash charging operation has not yet completed, control returns to thecommunication interrupt process shown in FIG. 22. If the Charge flag is1 (if YES at step S751), it is determined whether the sync mode settingdesignates the successive sync flash mode (step S753). If the sync modesetting designates the successive sync flash mode (if YES at step S753),it is determined whether the sync mode request requests the successivesync flash mode (step S754). If the sync mode request requests thesuccessive sync flash mode (if YES at step S754), it is determinedwhether the terminal Q has changed from “1” to “0” (step S755). If theterminal Q has not yet changed from “1” to “0” (if NO at step S755),control repeats the checking operation at step S755 until the terminal Qbecomes “0” to activate the flash device to discharge in response to thetrailing edge of the quench signal output from the terminal Q. If theterminal Q becomes “0” (if YES at step S755), control proceeds to stepS756. On the other hand, if it is determined at step S753 that the syncmode setting does not designate the successive sync flash mode, or if itis determined at step S754 that the sync mode request does not requestthe successive sync flash mode, control proceeds to step S756 toactivate the flash device to discharge in response to the trailing edgeof the signal output from the terminal X.

[0377] At step S756 it is determined whether the photometering modesetting designates the TTL photometering mode. If the photometering modesetting does not designate the TTL photometering mode (if NO at stepS756), control proceeds to step S768. On the other hand, if thephotometering mode setting designates the TTL photometering mode (if YESat step S756), the output port P4 of the flash CPU 65, i.e., the signal30Von, is set to “1” to thereby cause the 30-volt generating circuit 77to generate a voltage of 30 volts, the output port P5, i.e., the signalIGBTctl is set to “1” to switch the IGBT 83 ON via the level shiftcircuit 78, and the output port P3, i.e, the signal TRIGon is set to “1”to thereby cause the xenon flashtube 82 to start discharging (stepS757).

[0378] Subsequently, the timer B, which times the maximum flash emissionduration, is set to 3.2 ms and started (step S758). Subsequently, it isdetermined whether the terminal Q is “1” (step S759). If the terminal Qis not “1” (if NO at step S759), it is determined whether the timer-Blapsed flag is 1 (step S760). If the timer-B lapsed flag is not 1 (if NOat step S760), control returns to step S759 to repeat the operations atsteps S759 and S760. If the terminal Q is “1” (if YES at step S759), orif the timer-B lapsed flag is 1 (if YES at step S760) even if theterminal Q is not “1”, the output port P5, i.e., the signal IGBTctl isset to “0” to switch the IGBT 83 OFF via the level shift circuit 78, andat the same time, the output ports P3, i.e., the signal TRIGon and P4,i.e., the signal 30Von are reset to “0” (step S761). Subsequently, theremaining time of the timer B is stored in the RAM 65 a as a variable M1(step S762).

[0379] Subsequently, it is determined whether the timer-B lapsed flag is1 (step S763). If the timer-B lapsed flag is 1 (if YES at step S763),i.e., if the terminal Q does not become “1” before the timer B expires,“Far” is set as the photometering-range checking information (stepS764). The terminal Q does not become “1” before the timer B expireswhen the output of the operational amplifier 202 does not reach thepredetermined voltage T_ttl(x) because of the amount of the lightreceived by the TTL direct photometering sensor 23 being small.Therefore, when the terminal Q does not become “1” before the timer Bexpires, it is assumed that the photographic object is located at adistance farther from the range of flash photometering control of theflash device or that the reflectivity of the photographic object issmaller than a reference reflectivity. The set photometering-rangechecking information is transmitted to the camera body 10 in thecommunication information process at step S508.

[0380] If the timer-B lapsed flag is not 1 (if NO at step S763), it isdetermined whether the remaining time of the timer B, i.e., variable M1,which has been stored in the RAM 65 a is smaller than 30 μs (step S765).The time span 30 μs is the shortest time for the flash photometeringoperation with relative high precision from the moment the flash devicestarts discharges. If the remaining time of the timer B (variable M1)which has been stored in the RAM 65 a is smaller than 30 μs (if YES atstep S765), “Near” is set as the photometering-range checkinginformation (step S767). In this case, it is assumed that thephotographic object is located at a distance nearer to the range offlash photometering control of the flash device or that the reflectivityof the photographic object is greater than the reference reflectivity.If the remaining time of the timer B (variable M1) which has been storedin the RAM 65 a is not smaller than 30 μs (if NO at step S765), “Proper”is set as the photometering-range checking information (step S766). Inthis case, it is assumed that the photographic object is located at adistance within the range of flash photometering control of the flashdevice or that the reflectivity of the photographic object is about thesame as the reference reflectivity.

[0381] After “Proper”, “Near”, or “Far” has been set as thephotometering-range checking information, it is determined whether thevariable WLmode is 3 (step S768). If the variable WLmode is 3 (if YES atstep S768), a single low flash emission which serves as the main-flashemission command wireless signal is emitted to the slave flash device(step S769). If the variable WLmode is not 3 (if NO at step S768),control skips step S769, i.e., control proceeds straight from step S768to step S770. At step S770 the F_CRequest flag is set to 1, and controlreturns to the communication interrupt process shown in FIG. 22. In thepresent embodiment of the flash photography system, the single low flashemission which serves as the main-flash emission command wireless signalis emitted to the slave flash device at step S769 after the main flashdischarge has been completed, namely, after the TTL flash photometeringoperation performed during the operations at steps S757 through stepS761. This prevents the TTL flash photometering operation from beinginfluenced by the main-flash emission command wireless signal.

[0382]FIG. 30 is a graph showing the relationship between theaforementioned flash control time Tm [μs] and a flash emission amounterror [EV]. It can be understood from the graph that the error [EV] hasa tendency to increase as the flash control time Tm is shortened, due tothe time lag between the moment the xenon flashtube 82 is commanded tostop discharging and the moment the xenon flashtube 82 actually stopsdischarging, and other factors. In the present embodiment of the flashphotography system, the flash control time Tm with which the flashemission amount error becomes 1EV is set at 30 μs, and a state ofoverexposure is made known to the user by setting “Near” as thephotometering-range checking information if it is determined at stepS765 that the remaining time of the timer B is smaller than 30 μs. Thephotometering-range checking information is indicated on the informationdisplay panel 72 via the operation at step S510, and is transmitted tothe camera body 10 via the communication information process at stepS508 to be indicated on the information display panel 5 of the camerabody 10 via the indication process at step S104. Accordingly, the usercan visually check via either the information display panel 5 or theinformation display panel 72 if the flash photometering operation hasbeen performed properly.

[0383] [PWC Interrupt Process]

[0384] The PWC interrupt process will be hereinafter discussed in detailwith reference to the flow chart shown in FIGS. 27 and 28. The PWCinterrupt process is performed when the flash device 50 serves as slaveflash device (i.e., when the main switch 64 is in the WL position and atthe same time the wireless slave mode has been set via the wireless modesetting switch 63 c). The PWC interrupt process starts immediately afterthe amount of a low flash emission which is emitted by the built-inflash or the external flash device and subsequently received by thelight-receiving element 57 reaches a predetermined value.

[0385] In the PWC interrupt process, firstly a subsequent PWC interruptis disabled, and a PWC flag is set to 0 (step S850). Subsequently, it isdetermined whether the variable WLmode is 2 (step S851). If the variableWLmode is 2 (if YES at step S851), i.e., if in the old-system compatiblemode, an auto flash/ manual flash process is performed (step S852). Inthe auto flash/manual flash process, if the photometering mode requestrequests the auto flash photometering mode, the amount of light receivedby the light-receiving element 71 that is connected to the auto flashcircuit 70 is integrated (accumulated) by the auto flash circuit 70, andsubsequently the signal IGBTctl at the output port P5 is set to “0” tostop the discharge of the xenon flashtube 82 immediately after theintegrated light amount reaches a specified amount. On the other hand,in the auto flash/manual flash process, if the photometering moderequest requests the manual photometering mode, the xenon flashtube 82stops discharging immediately after a specified period of time elapses.After the auto flash/manual flash process is performed, an interrupt ofthe PWC counter is enabled (step S853), and control returns to the stepwhere the PWC interrupt occurs.

[0386] If the variable WLmode is not 2 (if NO at step S851), it isdetermined whether the variable WLstep is 2, i.e., it is determinedwhether the flash CPU 65 is in a standby state of receiving themain-flash emission command wireless signal (step S854). If the variableWLstep is not 2 (if NO at step S854), it is determined whether thevariable WLstep is 1, i.e., it is determined whether the flash CPU 65 isin a standby state of receiving the light-magnification command wirelesssignal (step S865). If the variable WLstep is not 1 either (if NO atstep S865), the variable WLstep is 0, thus indicating that the standbystate of receiving the main-flash emission command wireless signal. Inthis case, control proceeds from step S865 to step S877. At step S877the sync mode request is set as the sync mode setting. Subsequently, anappropriate process which corresponds to the value of the register PWCRthat represents the PWC counter value is performed (step S878 throughstep S890). The value of the register PWCR corresponds to the clockedinterval between two adjacent trailing edges of the received wirelesssignal serving as the pre-flash emission command wireless signal, andvaries in accordance with the pre-flash emission mode designated by theCPU 13 of the camera body (the first pre-flash emission mode or thesecond pre-flash emission mode) and the sync mode setting (see Table 6).

[0387] It is determined at step S878 whether the value of the registerPWCR is in the range of ±0.1 of 3.2 ms. If the value of the registerPWCR is in the range of ±0.1 of 3.2 ms (if YES at step S878), thepre-flash emission command wireless signal which designates thepre-flash emission mode PreM of “0” and a sync flash mode other than theflat emission mode (e.g., the leading curtain sync flash mode) has beenreceived, so that the pre-flash emission mode PreM is set to “0” (stepS879-1), and subsequently it is determined whether the sync mode settingdesignates the flat emission mode (step S879-2). If the sync modesetting designates the flat emission mode (if YES at step S879-2), thesync mode setting is changed from the flat emission mode to the leadingcurtain sync flash mode (step S879-3) and subsequently the variableWLstep is set to 1 while the flash mode setting is set to designate thepre-flash emission mode (step S884). Subsequently, the uniformflash-emission process shown in FIG. 25 is performed (step S887).Subsequently, an interrupt of the PWC timer is enabled (step S888) andcontrol returns to the step where the PWC interrupt occurs. If the syncmode setting does not designate the flat emission mode (if NO at stepS879-2), control proceeds straight from step S879-2 to step S884.

[0388] If the value of the register PWCR is out of the range of ±0.1 of3.2 ms (if NO at step S878), it is determined whether the value of theregister PWCR is in the range of ±0.1 of 4.2 ms (step S880). If thevalue of the register PWCR is in the range of ±0.1 of 4.2 ms (if YES atstep S880), the pre-flash emission command wireless signal whichdesignates the pre-flash emission mode PreM of “1” and a sync flash modeother than the flat emission mode (e.g., the leading curtain sync flashmode) has been received, so that the pre-flash emission mode PreM is setto “1” (step S881-1), and subsequently it is determined whether the syncmode setting designates the flat emission mode (step S881-2). If thesync mode setting designates the flat emission mode (if YES at stepS881-2), the sync mode setting is changed from the flat emission mode tothe leading curtain sync flash mode (step S881-3) and control proceedsto step S884 to perform the operations at steps S884 through step S888.If the sync mode setting does not designate the flat emission mode (ifNO at step S881-2), control proceeds straight from step S881-2 to stepS884.

[0389] If the value of the register PWCR is out of the range of ±0.1 of4.2 ms (if NO at step S880), it is determined whether the value of theregister PWCR is in the range of ±0.1 of 5.2 ms (step S882). If thevalue of the register PWCR is in the range of ±0.1 of 5.2 ms (if YES atstep S882), the pre-flash emission command wireless signal whichdesignates the pre-flash emission mode PreM of “1” and the flat emissionmode has been received, so that the pre-flash emission mode PreM is setto “1” (step S883-1), and subsequently it is determined whether the syncmode setting designates one of the leading curtain sync flash mode andthe successive sync flash mode (step S883-2). If the sync mode settingdesignates either the leading curtain sync flash mode or the successivesync flash mode (if YES at step S883-2), the sync mode setting ischanged to the flat emission mode (step S888-3) and subsequently controlproceeds to step S884 to perform the operations at steps S884 throughstep S888. If the sync mode setting does not designate either theleading curtain sync flash mode or the successive sync flash mode (if NOat step S883-2), control proceeds straight from step S883-2 to stepS884.

[0390] If the value of the register PWCR is out of the range of ±0.1 of5.2 ms (if NO at step S882), it is determined whether the value of theregister PWCR is in the range of ±0.1 of 6.2 ms (step S885). If thevalue of the register PWCR is in the range of ±0.1 of 6.2 ms (if YES atstep S885), the test-flash emission command wireless signal has beenreceived, so that the pre-flash emission mode PreM is set to “1”, thevariable WLstep is set to 0 because the main-flash emission commandwireless signal does not need to be received, and the flash mode settingis set to designate the test flash mode (step S886). Subsequently, theuniform flash-emission process shown in FIG. 25 is performed (stepS887). Subsequently, an interrupt of the PWC timer is enabled (stepS888) and control returns to the step where the PWC interrupt occurs.

[0391] If the value of the register PWCR is out of the range of ±0.1 of6.2 ms (if NO at step S885), i.e., if NO at each of steps S878, S880,S882 and S885, neither the pre-flash emission command wireless signalnor the test-flash emission command wireless signal has been received,so that the variable WLstep is set to 0 (step S889). Thereafter, themeasuring mode of the PWC timer is set to a mode of measuring aninterval between trailing edges of low flash emissions (wirelesssignals) that the light-receiving element 57 of the flash device 50receives, an interrupt of the PWC timer is enabled, and the PWC timer isstarted to thereby enter a state where wireless light signal (wirelesssignal) can be received (step S890). Subsequently, control returns tothe step where the PWC interrupt occurs. It is generally determined“YES” at one of steps S878, S880, S882 and S885. It is possible to bedetermined “NO” at step S885 if interfering light such as light emittedfrom a fluorescent lamp is received by the light-receiving element 57.

[0392] When control re-enters the PWC interrupt process after theoperation at step S884 has been performed and control has returned viathe operations at steps S887 and S888, the variable WLstep has been setto 1, namely, the pre-flash emission has been completed while the flashCPU 65 is in a standby state of receiving the light-magnificationcommand wireless signal. Therefore, when control re-enters the PWCinterrupt process after the operation at step S884 has been performedand control has returned via the operations at steps S887 and S888, itis determined “YES” at step S865, so that control proceeds to step S866to receive the light-magnification command wireless signal.

[0393] At step S866 it is determined whether the value of the registerPWCR is in the range of ±0.6 of 2.5 ms. If the value of the registerPWCR is out of the range of ±0.6 of 2.5 ms (if NO at step S866), thereceived wireless signal is not the light-magnification command wirelesssignal, so that control proceeds to step S877. If the value of theregister PWCR is in the range of ±0.6 of 2.5 ms (if YES at step S866),the flashlight-emitting magnification Mv1 is calculated at step S867using the following equation:

Mv1=((PWCR−2 ms)/16 μs)/8−5.

[0394] For instance, the flashlight-emitting magnification Mv1 is 0 (EV)when the value of the register PWCR is 2.640 ms.

[0395] Subsequently, the timer B is set for 3.1 ms, and is started (stepS868). Subsequently, it is determined whether the timer-B lapsed flag is1 (step S869). If the timer-B lapsed flag is not 1 (if NO at step S869),it is determined whether a PWC interrupt flag is 1 (step S870). If thePWC interrupt flag is not 1 (if NO at step S870), control returns tostep S869 to repeat the operations at steps S869 and S870. The PWCinterrupt flag is used to determine whether a wireless signal has beenreceived. Since the PWC interrupt is disabled when control enters theoperation at step S870, whether the third low flash emission that isrepresented by the third pulse (3) (shown in FIG. 6F) has been receivedis determined via the PWC interrupt flag.

[0396] If the PWC interrupt flag is 1 (if YES at step S870), the thirdlow flash emission that is represented by the third pulse (3) shown inFIG. 6F has been received, so that it is determined whether the value ofthe register PWCR is in the range of ±0.6 of 2.5 ms (step S871). If thevalue of the register PWCR is in the range of ±0.6 of 2.5 ms (if YES atstep S871), the flashlight-emitting magnification Mv2 is calculated atstep S872 using the following equation:

Mv2=((PWCR−2 ms)/16 μs)/8−5.

[0397] On the other hand, if the timer-B lapsed flag is 1 (if YES atstep S869), or if the value of the register PWCR is out of the range of±0.6 of 2.5 ms (if NO at step S871), the flashlight-emittingmagnification Mv2 is set at-5EV (step S873). This operation at step S873is performed when the wireless signal serving as the light-magnificationcommand wireless signal was not received or could not be receivedproperly.

[0398] After the flashlight-emitting magnification Mv2 is set at stepS872 or S873, the variable WLstep is set to 2 (step S874) andsubsequently it is determined whether the sync mode setting designatesthe flat emission mode (step S875). In the present embodiment of theflash photography system, the flash mode at the main exposure is set inaccordance with the sync mode setting designated by the pre-flashemission command wireless signal, and the main-flash emission commandwireless signal which corresponds to the set flash mode is transmittedto the slave flash device.

[0399] If the sync mode setting does not designate the flat emissionmode, the main flash discharge is performed in the normal flash emissionmode (in the light-magnification flash emission mode shown in FIG. 29).In this case, the built-in flash or the external flash device emits asingle low flash emission to transmit the same as the main-flashemission command wireless signal to the slave flash device. Therefore,if the sync mode setting does not designate the flat emission mode (ifNO at step S875), the measuring mode of the PWC timer is set to thecounter mode, an interrupt of the PWC timer is enabled, the registerPWCR that represents the PWC counter value is loaded with FFFF, and thePWC timer is started (step S876), and thereafter control returns to thestep where the PWC interrupt occurs. In the case where control returnsafter performing the operation at step S876, an interrupt of the PWCcounter occurs immediately after a single low flash emission is emittedby the built-in flash or the external flash device, and thereaftercontrol proceeds from step S855 to S856 via the operations at stepsS850, S851 and S854.

[0400] At step S856 the flashlight-emitting magnification Mv is set tothe flashlight-emitting magnification Mv1 which has been calculated atstep S867. Subsequently, it is determined whether the pre-flash emissionmode PreM is 1 (step S857). If the pre-flash emission mode PreM is 1 (ifYES at step S857), it is determined whether the sync mode requestrequests the successive sync flash mode (step S858). If the sync moderequest requests the successive sync flash mode (if YES at step S858),the flashlight-emitting magnification Mv is set to theflashlight-emitting magnification Mv2 obtained at step S872 or S873(step S859), and control proceeds to step S860. If the pre-flashemission mode PreM is not 1(if NO at step S857), or if the sync moderequest does not request the successive sync flash mode (if NO at stepS858) even if the pre-flash emission mode PreM is 1, control skips theoperation at step S859, so that control proceeds straight from step S857to S860 or from step S858 to S860. At step S860, a light-magnificationflash emission process (“Light-Magnification Flash Emission Process”shown in FIG. 29) is performed to emit the main flash emission.

[0401] On the other hand, if the sync mode setting designates the flatemission mode (if YES at step S875), the main flash discharge isperformed in the flat emission mode. In this case, the built-in flash orthe external flash device emits two successive low flash emissions totransmit the same as the main-flash emission command wireless signal tothe slave flash device. The interval between the two successive lowflash emissions corresponds to the uniform flash-emission duration Tfp.Therefore, if the sync mode setting designates the flat emission mode(if YES at step S875), an interrupt of the PWC timer is enabled (stepS888), and control returns to the step where the PWC interrupt occurs.In the case where control returns after performing the operation at stepS888, an interrupt of the PWC timer occurs immediately after the firstlow flash emission is received, and thereafter control proceeds fromstep S855 to S861 via the operations at steps S850, S851 and S854.

[0402] At step S861 it is determined whether the counter value of thePWC timer, or the value of the register PWCR, which represents theinterval between two successive low flash emissions serving as themain-flash emission command wireless signal, is in the range of ±0.6 of2.5 ms. If the value of the register PWCR is out of the range of ±0.6 of2.5 ms (if NO at step S861), control proceeds to step S865 without theuniform flash-emission process being performed. This is because thereceived main-flash emission command wireless signal does not correspondto the duration of the uniform flash-emission. On the other hand, if thevalue of the register PWCR is in the range of ±0.6 of 2.5 ms (if YES atstep S861), the uniform flash-emission duration Tfp (ms) is calculatedat step S862 using the following equation:

Tfp=(PWCR−2 ms)/64 μs (ms).

[0403] For instance, the uniform flash-emission duration Tfp is 10 mswhen the value of the register PWCR is 2.640 ms.

[0404] Subsequently, the flash mode setting is changed to the flatemission mode (step S863), and the uniform flash-emission process shownin FIG. 25 is performed to emit a uniform flash-emission as the mainflash emission (step S864).

[0405] After the main flash emission is completed at step S860 or S864,the variable WLstep is set to 0 (step S889), the measuring mode of thePWC timer is set to the mode of measuring an interval between trailingedges of low flash emissions (wireless signals) that the light-receivingelement 57 of the flash device 50 receives, an interrupt of the PWCtimer is enabled, and the PWC timer is started (step S890).

[0406] [Light-Magnification Flash Emission Process]

[0407] The light-magnification flash process performed at step S860 willbe hereinafter discussed in detail with reference to the flow chartshown in FIG. 29. In the light-magnification flash emission process,firstly each of the ports P5, P6 and P7 is set to serve as output portwhile a low-level signal “0” is output from each of the output ports P5,P6 and P7 (step S800). At this time, the electric charges accumulated inthe capacitor 73 are discharged via the resistor 74. Subsequently, theuniform flash-emission level Vfp is calculated at step S801 using thefollowing equation:

Vfp=Va×T_fire(zoom):

[0408] Subsequently, the output level of the voltage FPlvl, which is tobe output from the D/A conversion port Pda, is calculated at step S802using the following equation:

FPlvl=Kf×Vfp×2^(Mv)

[0409] wherein “Kf” represents a predetermined constant.

[0410] The calculated voltage FPlvl is output from the D/A conversionport Pda to be supplied to the non-inverting input terminal of thecomparator 75. Subsequently, the signal 30Von of the output port P4 ischanged from “0” to “1” so that a voltage of 30 volts is output from the30 volt generating circuit 77 to be applied to the level shift circuit78 (step S803). Subsequently, the output port P5, i.e., the signalIGBTctl, is changed from “0” to “1” (step S804) and subsequently theport P7 is set to serve as input port (step S805). A change of theoutput port P5, i.e., the signal IGBTctl, from “0 ” to “1” causes thevoltage of 30 volts generated by the 30-volt generating circuit 77 to beapplied to the gate IGBTg of an IGBT 83 to switch the IGBT 83 ON. In astate where the port P7 serves as input port, the photocurrent generatedby the light-receiving element 85 for detecting the amount of the flashemission discharged from the xenon flashtube 82 is accumulated in thecapacitor 73.

[0411] Subsequently, the signal TRIGon of the output port P3 is changedfrom “0” to “1” to thereby cause the xenon flashtube 82 to startdischarging (step S806), the timer B is set for 3.2 ms and started (stepS807), the port P5 (IGBTctl) is set to serve as input port (step S808),and the output port P3, i.e., the signal TRIGon, is set to “0” (stepS809).

[0412] Upon a commencement of the discharge of the xenon flashtube 82due to the operation at step S806, the light-receiving element 85generates a photocurrent which corresponds to the received light amount.The generated photocurrent is accumulated in the capacitor 73, whichincreases the voltage PDfl that is input to the inverting input terminalof the comparator 75. Thereafter, immediately after the voltage PDflreaches the voltage FPlvl, the output (IGBTctl) of the comparatorchanges from “1” to “0” to thereby switch the IGBT 83 OFF via the levelshift circuit 78. Consequently, the xenon flashtube 82 stopsdischarging. It should be noted that the light amount of the flash lightemission of the xenon flashtube 82 is proportional to 2^(Mv) since thevoltage FPlvl is determined as being proportional to 2^(Mv).

[0413] Subsequently, it is determined whether the timer-B lapsed flag is1 (step S810). If the timer-B lapsed flag is not 1 (if NO at step S810),control returns to step S810 to repeat the checking operation at stepS810 until the timer-B lapsed flag becomes 1. If the timer-B lapsed flagis 1 (if YES at step S810), each of the output ports P5 and P7 is set toserve as output port, and is set to “0”. At the same time, the port P4is set to “0”, while the port P6 is set to serve as input port (stepS811). Subsequently, the F_CRequest is set to 1 (step S812) and controlreturns to the PCW interrupt process shown in FIGS. 27 and 28.

[0414] [Old-System Process]

[0415] The old-system process performed at step S511-2 will behereinafter discussed in detail with reference to the flow chart shownin FIG. 32. In the old-system process, the charge completion signal andthe Fpulse signal that corresponds to the f-number set on the flashdevice 50 are transmitted to the camera body via the terminal connector56 if the camera body is a conventional type which cannot havecommunication with the flash CPU 65. The Fpulse signal is a pulse signalhaving a frequency proportional to the camera's f-number setting set onthe flash device 50.

[0416] In the old-system process, firstly it is determined whether theF_COn flag is 1 (step S900). If the F_COn flag is 1 (if YES at stepS900), control returns to the flash main process shown in FIG. 20because the camera body is of a type which can have communication withthe flash CPU 65 (see step S613 in FIG. 22). If the F_COn flag is not 1(if NO at step S900), it is determined whether the WLset flag is 1 (stepS901). If the WLset flag is 1 (if YES at step S901), control returns tothe flash main process shown in FIG. 20 because the flash device 50 isserving as slave flash unit (see step S562 in FIG. 21).

[0417] If the F_COn flag is not 1 (if NO at step S900) and further ifthe WLset flag is not 1 (if NO at step S901), each of the ports Pd2 andPd3 (see FIG. 33) of the flash CPU 65 is set to serve as output port(step S902). It should be noted that setting each of the ports Pd2 andPd3 of the flash CPU 65 to serve as output port indicates that the I/Oport switch terminal IN/OUT (see FIG. 34) is changed from “1” to “0”.

[0418] Subsequently, it is determined whether the Charge flag is 1 (stepS903). The Charge flag is set to 1 when the main capacitor 79 has beenfully charged. If the Charge flag is 1 (if YES at step S903), the I/Oport Pd2 of the flash CPU 65 is set to 1 while a signal of “1” is outputtherefrom (step S904). Due to the operation at step S904, the chargecompletion signal “1” is output to the CPU 13 of the camera body 10 viathe terminal R. On the other hand, if the Charge flag is not 1 (if NO atstep S903), the I/O port Pd2 of the flash CPU 65 is set to 0 and asignal of “0” is output therefrom (step S905). Due to the operation atstep S905, the charge completion signal “0” is output to the CPU 13 ofthe camera body 10 via the terminal R.

[0419] After the charge completion signal “0” or “1” has been output tothe CPU 13, the Fpulse signal is output from the port Pd3 (step S906)and subsequently control returns to the flash main process shown in FIG.20.

[0420]FIG. 35 is a timing chart for the signals output from theterminals C, R, Q and X of the terminal connector 56 and for a flashemission in the old-system process. When the terminal C of the terminalconnector 56 of the camera body 10 is “0”, upon a change of the chargecompletion signal from “0” to “1”, the terminal R changes from “0” to“1”. This causes the Fpulse signal to be output from the terminal Q (ata time (a) shown in FIG. 35). Thereafter, upon a change of the terminalX from “1” to “0” (at a time (b) shown in FIG. 35), the flash device 50starts discharging, and at the same time, the terminal Q is set to serveas input port. Thereafter, the flash device 50 stops discharging inresponse to the quench signal transmitted from the camera body 10 viathe terminal Q (at a time (c) shown in FIG. 35).

[0421] As can be understood from the above description, it is possibleto achieve an ideal pre-flash emission in accordance with a sync mode,even in the case where a plurality of flash devices are used inmulti-flash photography. Furthermore, according to the presentinvention, the slave flash device(s) can be controlled by a plurality ofemission timings via a single pre-flash emission command signal.Accordingly, since it is unnecessary to transmit a pre-flash emissioncommand signals for each slave-flash emission timing, the electricalpower loss due to the excessive operation of the trigger circuit, uponthe pre-flash emission command signal being transmitted, can besubstantially reduced.

[0422] Obvious changes may be made in the specific embodiments of thepresent invention described herein, such modifications being within thespirit and scope of the invention claimed. It is indicated that allmatter contained herein is illustrative and does not limit the scope ofthe present invention.

What is claimed is:
 1. A flash photography system having a camera bodyand a plurality of external flash devices electrically connected to saidcamera body, said plurality of external flash devices being activated toemit a preliminary flash emission before a main flash emission, saidcamera body comprising: a designating device for designating a syncflash mode for said main flash emission from among at least one syncflash mode; a first pre-flash emission mode in which said plurality ofexternal flash devices are activated to emit said preliminary flashemission at the same time; a second pre-flash emission mode in whichsaid plurality of external flash devices are activated to emit saidpreliminary flash emission in a predetermined order; and a pre-flashemission mode selecting device which selects one of said first pre-flashemission mode and said second pre-flash emission mode in accordance withthe designated sync flash mode.
 2. The flash photography systemaccording to claim 1, wherein said at least one sync flash mode includesa successive sync flash mode in which said plurality of external flashdevices are activated to discharge in a predetermined emission sequence,and wherein said pre-flash emission mode selecting device selects saidsecond pre-flash emission mode in said successive sync flash mode,wherein said pre-flash emission mode selecting device selects said firstpre-flash emission mode when not in said successive sync flash mode. 3.The flash photography system according to claim 1, wherein each of saidplurality of external flash devices comprises a sync mode requestsetting device for manually selecting a sync flash mode as a sync moderequest, wherein said sync mode request is transmitted to saiddesignating device of said camera body to request said each externalflash device to discharge in said selected sync flash mode; and whereinsaid designating device designates a sync flash mode for said main flashemission in accordance with said sync mode requests set by said syncmode request setting device of each of said plurality of external flashdevices.
 4. The flash photography system according to claim 3, wherein,in the case where said second pre-flash emission mode is selected, saidplurality of external flash devices are activated to emit saidpreliminary flash emission in said predetermined order in the sync flashmode selected according to said sync mode request.
 5. A flashphotography system having a camera body, at least one external flashdevice which is electrically connected to said camera body, and at leastone slave flash device, wherein said at least one external flash deviceand said at least one slave flash device are activated to emit apreliminary flash emission before a main flash emission, said flashphotography system comprising: a designating device for designating async flash mode for said main flash emission; a first pre-flash emissionmode in which said at least one external flash device and said at leastone slave flash device are activated to emit said preliminary flashemission at the same time; a second pre-flash emission mode in whichsaid at least one external flash device and said at least one slaveflash device are activated to emit said preliminary flash emission in apredetermined order; a pre-flash emission command device including afirst command device which transmits a first command signal to said atleast one external flash device; and a second command device whichactivates said at least one external flash device to emit a low flashemission serving as a second command signal to transmit said secondcommand signal to said at least one slave flash device; and a pre-flashemission mode selecting device which selects one of said first pre-flashemission mode and said second pre-flash emission mode; wherein saidpre-flash emission mode selecting device selects one of said firstpre-flash emission mode and said second pre-flash emission mode inaccordance with said sync flash mode designated by said designatingdevice in the case where only said first command device transmits saidfirst command signal to said at least one external flash device; andwherein said pre-flash emission mode selecting device selects saidsecond pre-flash emission mode regardless of said sync flash modedesignated by said designating device in the case where said secondcommand device activates said at least one external flash device to emitsaid low flash emission.
 6. The flash photography system according toclaim 5, wherein, in the case where said first pre-flash emission modeis selected, said pre-flash emission command device controls an outputtiming of said first command signal and said second command signal sothat said at least one external flash device and said at least one slaveflash device are activated to emit said preliminary flash emission atthe same time.
 7. The flash photography system according to claim 6,wherein said second command signal is specified by at least one timeinterval of at least two low flash emissions emitted by one of said atleast one external flash device; and wherein said second command deviceactivates said at least one external flash device to emit said low flashemission at an emission interval according to one of said first andsecond said pre-flash emission modes selected by said pre-flash emissionmode selecting device.
 8. The flash photography system according toclaim 7, wherein said pre-flash emission command device furthercomprises a timer which expires after a predetermined period of time;wherein, in said first pre-flash emission mode, said timer is started,while said at least one external flash device is activated via saidsecond command device to emit said low flash emission serving as saidsecond command signal; said first command signal is transmitted to saidat least one external flash device via said first command device uponexpiration of said timer; and said at least one external flash device isactivated again via said second command device to emit said low flashemission, serving as said second command signal, at the same time saidtransmission of said first command signal to said at least one externalflash device is completed.
 9. The flash photography system according toclaim 8, wherein said predetermined period of time is determined inaccordance with a duration of said low flash emission which is emittedby said at least one external device via said second command device, anda time necessary for said first command device to complete saidtransmission of said first command signal to said at least one externalflash device.
 10. The flash photography system according to claim 5,wherein each of said at least one external flash device and each of saidat least one slave flash device comprises a sync mode request settingdevice for manually selecting a sync flash mode as a sync mode request;wherein, in the case where said first pre-flash emission mode isselected, said at least one external flash device and said at least oneslave flash device are activated to emit said preliminary flash emissionat the same time regardless of said sync mode request; and wherein, inthe case where said second pre-flash emission mode is selected, said atleast one external flash device and said at least one slave flash deviceare activated to emit said preliminary flash emission in saidpredetermined order in said selected sync flash mode set as said syncmode request.
 11. The flash photography system according to claim 10,wherein said designating device designates said sync flash mode for saidmain flash emission in accordance with said sync mode requests set bysaid sync mode request setting device of each of said plurality ofexternal flash devices.
 12. The flash photography system according toclaim 5, wherein said designating device, said pre-flash emission modeselecting device and said pre-flash emission command device are providedin said camera body.
 13. The flash photography system according to claim5, wherein said designating device, said pre-flash emission modeselecting device and said first command device of said pre-flashemission command device are provided in said camera body, and whereinsaid second command device of said pre-flash emission command device isprovided in said at least one external flash device.
 14. A flashphotography system having a camera body, a built-in flash incorporatedin said camera body, at least one external flash device which iselectrically connected to said camera body, and at least one slave flashdevice, wherein said at least one external flash device and said atleast one slave flash device are activated to emit a preliminary flashemission before a main flash emission, said flash photography systemcomprising: a designating device for designating a sync flash mode forsaid main flash emission; a first pre-flash emission mode in which saidat least one external flash device and said at least one slave flashdevice are activated to emit said preliminary flash emission at the sametime; a second pre-flash emission mode in which said at least oneexternal flash device and said at least one slave flash device areactivated to emit said preliminary flash emission in a predeterminedorder; a pre-flash emission mode selecting device which selects one ofsaid first pre-flash emission mode and said second pre-flash emissionmode; a built-in flash emission mode setting device for determiningwhether said built-in flash one of discharges and does not discharge atsaid main flash emission, for an exposure operation; and a pre-flashemission command device including a first command device which transmitsa first command signal to said at least one external flash device; and asecond command device which activates one of said built-in flash andsaid at least one external flash device to emit a low flash emissionserving as a second command signal to transmit said second commandsignal to said at least one slave flash device; wherein said pre-flashemission mode selecting device selects one of said first pre-flashemission mode and said second pre-flash emission mode in accordance withsaid sync flash mode designated by said designating device in the casewhere only said first command device transmits said first command signalto said at least one external flash device; wherein, in the case wheresaid second command device activates one of said built-in flash and saidat least one external flash device to emit a low flash emission whereinsaid built-in flash emission mode setting device determines saidbuilt-in flash to discharge at said main flash emission for an exposureoperation, said pre-flash emission mode selecting device selects saidfirst pre-flash emission mode regardless of said sync flash modedesignated by said designating device; and wherein in the case wheresaid second command device activates one of said built-in flash and saidat least one external flash device to emit a low flash emission whereinsaid built-in flash emission mode setting device determines saidbuilt-in flash not to discharge at said main flash emission for anexposure operation, said pre-flash emission mode selecting deviceselects said second pre-flash emission mode regardless of said syncflash mode designated by said designating device.
 15. The flashphotography system according to claim 14, wherein, in the case wheresaid first pre-flash emission mode is selected, said pre-flash emissioncommand device controls an output timing of said first command signaland said second command signal so that said at least one external flashdevice and said at least one slave flash device are activated to emitsaid preliminary flash emission at the same time.
 16. The flashphotography system according to claim 15, wherein said second commandsignal is specified by at least one time interval of at least two lowflash emissions emitted by one of said at least one external flashdevice and said built-in flash; and wherein said second command deviceactivates one of said built-in flash and said at least one externalflash device to emit said low flash emission at an emission intervalaccording to one of said first and second said pre-flash emission modesselected by said pre-flash emission mode selecting device.
 17. The flashphotography system according to claim 16, wherein said pre-flashemission command device further comprises a timer which expires after apredetermined period of time; wherein, in said first pre-flash emissionmode, said timer is started, while one of said built-in flash and saidat least one external flash device is activated via said second commanddevice to emit said low flash emission serving as said second commandsignal; said first command signal is transmitted to said at least oneexternal flash device via said first command device upon expiration ofsaid timer; and said one of said built-in flash and at least oneexternal flash device is activated again via said second command deviceto emit said low flash emission, serving as said second command signal,at the same time said transmission of said first command signal to saidat least one external flash device is completed.
 18. The flashphotography system according to claim 17, wherein said predeterminedperiod of time is determined in accordance with a duration of said lowflash emission which is emitted by said at least one external device viasaid second command device, and a time necessary for said first commanddevice to complete said transmission of said first command signal tosaid at least one external flash device.
 19. The flash photographysystem according to claim 14, wherein each of said at least one slaveflash device comprises: a sync mode request setting device for manuallyselecting a sync flash mode as a sync mode request; a photoreceiverwhich receives said low flash emission emitted by said one of saidbuilt-in flash and said at least one external flash device; a measuringdevice which measures a duration of said low flash emission; a detectingdevice which determines which of said first pre-flash emission mode andsaid second pre-flash emission mode has been selected, based on whethersaid duration of low flash emission is a first duration which representssaid first pre-flash emission mode, and determines whether said durationof low flash emission is a second duration which represents said secondpre-flash emission mode; and an emission control device which activatessaid slave flash device to emit said preliminary flash emissionsimultaneously with said preliminary flash emission emitted by said atleast one external flash device regardless of said sync mode request inthe case where said first pre-flash emission mode is selected; whereinsaid sync mode request is transmitted to said emission control device torequest said slave flash device to discharge in said selected sync flashmode; and wherein, in the case where said second pre-flash emission modeis selected, said emission control device activates said slave flashdevice to emit said preliminary flash emission in the sync flash modeselected according to said sync mode request.
 20. The flash photographysystem according to claim 14, wherein said at least one external flashdevice also comprises a sync mode request setting device for manuallyselecting a sync flash mode as a sync mode request, wherein said syncmode request is transmitted to said designating device to request saidcorresponding each external flash device to discharge in said selectedsync flash mode; wherein said designating device designates said syncflash mode for said main flash emission in accordance with said syncmode requests selected by each of said at least one external flashdevice.
 21. The flash photography system according to claim 14, whereinsaid designating device, said pre-flash emission mode selecting device,said built-in flash emission mode setting device, and said pre-flashemission command device are provided in said camera body.
 22. The flashphotography system according to claim 14, wherein said designatingdevice, said pre-flash emission mode selecting device, said built-inflash emission mode setting device, and said first command device ofsaid pre-flash emission command device are provided in said camera body,and wherein said second command device of said pre-flash emissioncommand device is provided in said at least one external flash device.23. A flash photography system having a camera body, a built-in flashincorporated in said camera body, and a plurality of slave flashdevices, wherein said plurality of slave flash devices are activated toemit a preliminary flash emission before a main flash emission, saidcamera body comprising: a first pre-flash emission mode in which saidplurality of slave flash device are activated to emit said preliminaryflash emission at the same time; a second pre-flash emission mode inwhich said plurality of slave flash device are activated to emit saidpreliminary flash emission in a predetermined order; a pre-flashemission mode selecting device which selects one of said first pre-flashemission mode and said second pre-flash emission mode; a built-in flashemission mode setting device for determining whether said built-in flashone of discharges and does not discharge at said main flash emission,for an exposure operation; and a pre-flash emission command device whichactivates said built-in flash to emit a low flash emission serving as acommand signal to transmit said command signal to said plurality ofslave flash device; wherein, in the case where said built-in flashemission mode setting device determines said built-in flash to dischargeat said main flash emission for an exposure operation, said pre-flashemission mode selecting device selects said first pre-flash emissionmode; and wherein, in the case where said built-in flash emission modesetting device determines said built-in flash not to discharge at saidmain flash emission for an exposure operation, said pre-flash emissionmode selecting device selects said second pre-flash emission mode. 24.The flash photography system according to claim 23, wherein said commandsignal is specified by at least one time interval of at least two lowflash emissions emitted by said built-in flash; and wherein saidpre-flash emission command device activates said built-in flash to emitsaid low flash emission at an emission interval according to one of saidfirst and second said pre-flash emission modes selected by saidpre-flash emission mode selecting device.
 25. The flash photographysystem according to claim 23, wherein each of said plurality of slaveflash device comprises: a sync mode request setting device for manuallyselecting a sync flash mode as a sync mode request; a photoreceiverwhich receives said low flash emission emitted by said built-in flash; ameasuring device which measures a duration of said low flash emission; adetecting device which determines which of said first pre-flash emissionmode and said second pre-flash emission mode has been selected, based onwhether said duration of low flash emission is a first duration whichrepresents said first pre-flash emission mode, and determines whethersaid duration of low flash emission is a second duration whichrepresents said second pre-flash emission mode; and an emission controldevice which activates said slave flash device to emit said preliminaryflash emission simultaneously with said preliminary flash emissionemitted by another slave flash device regardless of said sync moderequest in the case where said first pre-flash emission mode isselected; wherein said sync mode request is transmitted to said emissioncontrol device to request said slave flash device to discharge in saidselected sync flash mode; and wherein, in the case where said secondpre-flash emission mode is selected, said emission control deviceactivates said slave flash device to emit said preliminary flashemission in the sync flash mode selected according to said sync moderequest.
 26. A camera comprising: at least one terminal connector viawhich a plurality of external flash devices are electrically connectedto said camera; a designating device for designating a sync flash modefor a main flash emission from among at least one sync flash mode; afirst pre-flash emission mode in which a plurality of flash devices areactivated to emit said preliminary flash emission at the same timebefore said main flash emission; a second pre-flash emission mode inwhich a plurality of flash devices are activated to emit saidpreliminary flash emission in a predetermined order before said mainflash emission; a pre-flash emission mode selecting device which selectsone of said first pre-flash emission mode and said second pre-flashemission mode in accordance with the designated sync flash mode; and apre-flash emission command device which commands said plurality of flashdevices to emit said preliminary flash emission in one of said firstpre-flash emission mode and said second pre-flash emission mode which isselected by said pre-flash emission mode selecting device.
 27. Thecamera according to claim 26, wherein said at least one sync flash modecomprises a successive sync flash mode in which said plurality of flashdevices are activated to discharge in a predetermined emission sequence;and wherein said pre-flash emission mode selecting device selects saidsecond pre-flash emission mode in said successive sync flash mode,wherein said pre-flash emission mode selecting device selects said firstpre-flash emission mode when mot in said successive sync flash mode. 28.The camera according to claim 26, wherein said pre-flash emissioncommand device comprises: a first command device which transmits a firstcommand signal to at least one external flash device via said terminalconnector; and a second command device which activates one of said atleast one external flash device to emit a low flash emission serving asa second command signal to transmit said second command signal to atleast one slave flash device; wherein said pre-flash emission modeselecting device selects one of said first pre-flash emission mode andsaid second pre-flash emission mode in accordance with the designatedsync flash mode in the case where only said first command devicetransmits said first command signal to said at least one external flashdevice; and wherein said pre-flash emission mode selecting deviceselects said second pre-flash emission mode in the case where saidsecond command device activates one of said at least one external flashdevice to emit a low flash emission.
 29. The camera according to claim28, wherein said camera further comprises: a built-in flash incorporatedin said camera; and a built-in flash emission mode setting device fordetermining whether said built-in flash one of discharges and does notdischarge at said main flash emission, for an exposure operation;wherein said second command device activates one of said built-in flashand said at least one external flash device to emit a low flash emissionserving as said second command signal; wherein, in the case where saidsecond command device activates one of said built-in flash and said atleast one external flash device to emit a low flash emission whereinsaid built-in flash emission mode setting device determines saidbuilt-in flash to discharge at said main flash emission for an exposureoperation, said pre-flash emission mode selecting device selects saidfirst pre-flash emission mode; and wherein, in the case where saidsecond command device activates one of said built-in flash and said atleast one external flash device to emit a low flash emission whereinsaid built-in flash emission mode setting device determines saidbuilt-in flash not to discharge at said main flash emission for anexposure operation, said pre-flash emission mode selecting deviceselects said second pre-flash emission mode.
 30. The camera according toclaim 29, wherein, in the case where said first pre-flash emission modeis selected, said pre-flash emission command device controls an outputtiming of said first command signal and said second command signal sothat said at least one external flash device and said at least one slaveflash device are activated to emit said preliminary flash emission atthe same time.
 31. The flash photography system according to claim 30,wherein said second command signal is specified by at least one timeinterval of at least two low flash emissions emitted by one of said atleast one external flash device and said built-in flash; and whereinsaid second command device activates said at least one external flashdevice to emit said low flash emission at an emission interval accordingto one of said first and second said pre-flash emission modes selectedby said pre-flash emission mode selecting device.
 32. The flashphotography system according to claim 31, wherein said pre-flashemission command device further comprises a timer which expires after apredetermined period of time; wherein, in said first pre-flash emissionmode said timer is started, while one of said built-in flash and said atleast one external flash device is activated via said second commanddevice to emit said low flash emission serving as said second commandsignal; said first command signal is transmitted to said at least oneexternal flash device via said first command device upon expiration ofsaid timer; and one of said built-in flash and said at least oneexternal flash device is activated again via said second command deviceto emit said low flash emission serving as said second command signal,at the same time said transmission of said first command signal to saidat least one external flash device is completed.
 33. The flashphotography system according to claim 32, wherein said predeterminedperiod of time is determined in accordance with a duration of said lowflash emission which is emitted by said at least one external device viasaid second command device, and a time necessary for said first commanddevice to complete said transmission of said first command signal tosaid at least one external flash device.
 34. A flash device comprising:a sync mode request setting device for manually selecting a sync flashmode as a sync mode request; a photoreceiver which receives a low flashemission serving as a command which is emitted by a light source of saidcamera body; a measuring device which measures a duration of said lowflash emission; a first pre-flash emission mode in which said flashdevice and another at least one flash device are activated to emit apreliminary flash emission at the same time; a second pre-flash emissionmode in which said flash device and said another at least one flashdevice are activated to emit said preliminary flash emission in apredetermined order; a pre-flash emission mode selecting device whichselects one of said first pre-flash emission mode and said secondpre-flash emission mode; and a detecting device which determines whethersaid duration is a first duration which represents said first pre-flashemission mode and further determines whether said duration of low flashemission is a second duration which represents said first pre-flashemission mode to determine which of said first pre-flash emission modeand said second pre-flash emission mode has been selected by saidpre-flash emission mode selecting device; an emission control devicewhich activates said flash device to emit said preliminary flashemission simultaneously with said preliminary flash emission emitted bysaid another at least one flash device regardless of said sync moderequest in the case where said first pre-flash emission mode isselected; wherein said sync mode request is transmitted to said emissioncontrol device to request said flash device to discharge in saidselected sync flash mode; wherein, in the case where said secondpre-flash emission mode is selected, said emission control deviceactivates said flash device to emit said preliminary flash emission inthe sync flash mode selected according to said sync mode request.